I wouldn't bother.
I have a '67 F-250 4WD that I put a 453 Detroit in, back in '76. Believe me, it is the wrong choice...the bare block is 1200#. Lots of fabrication to make it fit.
I mated it to a New Process 435 4speed, with a warner OD unit in front of the 435. Lots of gears! I pulled a 5thW trailer all over the US with it. It was quite a talking piece in it's day. I still have the truck...use it as a yard donkey!
Back then you couldn't get a diesel in a pickup. Now there are many choices. I have a second generation Dodge with the CTD and an '06 GMC Duramax. The Duramax beats all the others, hands down. I would opt for a LBZ Duramax/Allison. You will be much happier.
'06 GMC Duramax/Allison 3500, CC, LB, DRW
'94 Dodge Ram CTD, 2500, Std Cab, LB, SRW
K1200RS & FJR1300A