OK, I'm dumb, need help

What year is your truck and how is it presently outfitted? You could get the great big iron anchor HD slant six bellhousing that came in front of the NP435 transmission, it uses an 11 inch clutch. Also a small block flywheel only needs one hole drilled in it to make it usable on a \6, a lot of slant six racers do this for an SFI flywheel, which is a must for any performance build.