340 Stroker Build Need LOTS of Advice

Seriously 245s with a 416?
Shoot; a hot 318will melt those to 40/50 mph. A hot 360 will break 'em loose at 50plus in second gear with 3.55s
That needs a rethink right there or the stroker IMO is a colossal misapplication. I had to go to 295s to get even a small semblance of traction with my 367. Even 325s spin thru two gears, in my 68 Barracuda at 3650 street pounds..
A Duster has the same basic rear tub size, so .............why in the world 245s. That's got to be a typo......lol.
The Wallace calculator has an interesting bit of math, that correlates your cylinder pressure and volume into a ratio that is useful to estimate low rpm performance. When I input the required numbers for my engine,it spits out a VP ratio of 148 or more, which I know is a tire-shredder . A bet strokers start at close to 180, which makes it 180/148= about 22% more powerful than mine, in that rpm range. So If I can spin 295s thru 2 gears,and well into third gear; imagine when the stroker will stop spinning, with 245s,lol.
At least mine spins in a straight line,lol. When I had 245s on it, that car was mostly out of control. It did things to me that were down right savage. 275s were not much different, sending me in circles at the slightest provocation. 295s are manageable, for this old cowboy..
My 325s are best, but they rub a bit on the inboard sidewalls, around turns, with a bit too much throttle,so like most of the time,lol..But they do pretty good in a straight line.Plus I'm not fond of the dance they do back there on slow turns.But most of that is my fault for putting them on 10s.
In any case, you need to address the rear suspension .