7 1/4 to 8 3/4 rear end swap info needed

do you remember how much exactly you had to shorten your driveshaft? i have a great drivshaft mechanic that is cheap and will shorten my drievshaft like he did when i swapped from /6 to 318/727. when i was in the process of doing that swap, someone on faro told me the exact length to cut my driveshaft and it worked out great.

on another note...should i buy new shock plates(as in not used)? or are original ones okay to use?
if i buy new shock plates and u bolts, does anyone have a good parts store to recommend?

p.s. my dart is a swinger

thanks for all the great info guys! this is very helpful