I have the ep381 in my 85 with 87 tank with a 383 with 500 hp works great no problem with enough fuel. Been on chassis dyno with a good tuner he said it was fine.
My 85 was set up for towing. Had the 3 speed with granny hear. Pulled my drag cars with it. It had 2 piece shaft. I sold my drag car . put a turbo 400. With 383 stroker one piece shaft. Back halfed the rear with 31x16 MT tires is now a Pro Street. Everything works great.
my name is David have a 85 Pro street C-10 with a 383 turbo 400 with coil overs and ladder bars tubbed
with original tubs. mickey thompson 31x16 tires. and 15x5 on the front weld wheels