either way, it is 440. cast or forged crank.
I recommend the Hughes Whiplash cam for the low comp smog head MH engine to wake it right up with a stock TC/gears.
I used a 78 MH 440 in my 88 d150 with the whiplash cam. = awesome street engine for daily driving in traffic. scares everybody at the gas pumps at an idle.
large plug or peanut plug heads are fine. I have had both on mine.
mine had about 40,000 miles on the clock and now has about 84,000 with 10,000 on the whiplash cam.
wish I could run up on another one for a spare. grab it while you can IMHO.