Can't get Pro Parts headers to fit.

The centerline of the crankshaft should be 5 1/4" from the top of the k-frame.
So, if I measure and the engine is low, what is the proper way to raise the engine?
The crankshaft centerline should be 2 1/2" from driver side frame rail and 1 1/4 from passenger rail
I spent some time looking for my old install posts, nada, here goes.
I haven't put in fenderwell in a long time but to shift the engine around, take the weight of the engine off the mounts with a floor jack, with board to protect the pan, start by loosening all the bolts/nuts holding the mount brackets to the engine and loosen the bolt thru the k-frame, then use a bar, fl jack handle, whatever's nec to shift motor towards where you need it, wedge it there till you tighten everything you loosened. There are 318 van/truck rubber insulators that are approc 1/4 in thicker if you need height. As mentioned, shims can be made and used.
Sometimes loosening/shifting/raising the trans mount can help.
Get the motor close, then I would do driver side, I think, lol.
A lot depends on how " bent " your car is since factory.
It can be very challenging to avoid having to ding a tube, but I haven't put in fenderwells since . . .
Good luck.
I'm using the Schumachers on a 6cyl K-Frame as well.
How can you shim the mount? You mean go up with the engine by throwing a washer under the motor mount (can you do that? does that weaken the mount?)? I can't do this anyway because the header tubes that wrap around the driver's side frame rail will also go up and hit the frame. Thus no room to go up with the engine.

I guess my only recourse would be to keep on cutting or call ProParts to see if my header bend is messed up. (if they even exist anymore).
Schumacher sells a shim pack. The kit should come with a bunch of shims that fit under the mount. Different sizes which add up to over 1" of shims.

shim pack.jpg
Schumacher sells a shim pack. The kit should come with a bunch of shims that fit under the mount. Different sizes which add up to over 1" of shims.

View attachment 1716172700
i made some oversize 'fender shims' to space the mounts on my valiant when i swapped from /6 to small block. worked a treat and only had to loosen the mount, lift the motor and slip them in.
Schumacher sells a shim pack. The kit should come with a bunch of shims that fit under the mount. Different sizes which add up to over 1" of shims.

View attachment 1716172700
These shims look great!
I just hope that I can raise the engine enough before the header tubes that curl under the frame actually start to hit the frame.

Question: If I shim one side, do I have to shim the other side an equal amount? Or can I shim one side without touching the other?
I only shimmed 1 side on mine and it worked just fine.
My experience with Schumacher mounts, albeit to a small block K, was this to get my engine centered was this;

Put engine in with trans originally, could not get it centered to save my life. Tried shims that came with my schumacher tri y's, no go. It was not off much, so I felt leave it for break in and fix after.

Had to pull engine for a noise, fixed it and reinstalled. Just pulled and reinstalled the engine only, trans stayed this time.

My engine went in perfectly centered as I lowered down about 1.5 inches away from the trans, made sure trans was jacked up perfect and straight, made sure engine was level, then pushed engine from the front and it slammed into the trans perfect and is 100% level now.

Probably a useless post from a newbie, but I found that the biscuits sideways act like sliders without the trans dragging it at the end and allowed for lots of alignment before final mating of the two.
pretty sure tti makes those these days. are you sure the engine is in th eproper position? over the years i've installed a few sets of proparts (well before tti started making them). mine weren't step headers like that. they were the same size primary all the way. driver side was always pretty easy to install. i could put the headers one and off without moving the engine at all. it is possible they their bend isn't exactly correct. years ago after installing a set for a friend i went to put a set on one of my cars and the one that loops over the steering column (#7) wouldn't fit. i couldn't figure out why because i had just installed a set not long before.. turns out that they had a bad batch where that one pipe was aflatter turn then the set i installed on my friends... i ended up contacting proparts, they had me mark where the tube was hitting and send it back. aure enough the pipe was wrong. they sent me a new properly bent pipe.
STOP right there! Exactly my thoughts before reading any of the other posts but glancing at the pics. ENGINE position.
Engine position results:

Measured where my engine position is and it matches the numbers on the reference table perfectly. Engine is sitting where it should be.

Dumb ProParts headers still don’t fit. Feel like I’ve wasted so much time and money and beginning to think I just don’t have the skill for this engine swap.

Guess I’ll just keep on cutting until there’s nothing left of the fenderwells. Don’t care anymore. Stupid cars. So frustrated. Been working for so many months on this thing. Thought buying good headers would help. Absolutely no progress at all (as usual).