Giving Up?

Hang on, do not take the trans down!

Firstly, you have .060 departure........... in how many places? .060 is more than adequate, IF it's .060 all around and the daymn thing stops spinning! The disc has to stop spinning! If the disc has stopped spinning the N-R shift cannot grind.If the disc has stopped spinning then the N to 1st pops right in.

Wait for it..... the reverse is also true,lol. If the disc does NOT stop spinning with the vehicle stopped, it HAS to grind into reverse and it HAS to to be impossible to shift into first. It cannot be otherwise.
SO
figure out why the disc is not coming to a stop, and your problems are over.

Try .080,lol.

IF you have had an align-bore or align-hone, OR, if the bell is not original to the engine, OR the bell hole is bigger than the retainer, OR the bell was at one time welded on, Or the bell is broken; THEN the bell has to be re-centered to the crankshaft.If you don't do that then it is possible that the crank centerline is not concentric with the trans centerline, and sooooo they end up at an angle to eachother, and the disc drags in at least two places; one on the backside and one on the front side. Soooo you can have .060 in ONE place and ZERO in another, on the one side, and 180* later the same on the otherside, for an average of ZERO,lol.
It is also possible for the input shaft to be dragging in the pilot bushing; or to be jammed into the back of the crank.
SO
figure out why the disc is not coming to a stop, and your problems are over.