Yep, got my book, and it IS neat!

Lots of info and Pictures on ID'ing blocks and differences between them and much more.

I did not know there were a standard and then Heavy duty engines in these sizes. Still readin'....
4L80E trans will need 'puter to run it. Don't know what the spicer is, but bet you can't find a bellhouse for it and your new six. What's wrong with a SM465 4spd used from 68 to 90something? OR, maybe the later model OD NVG unit used now, if you can find the bellhouse for it. The bolt-up to engine is same for GM, but some clutches were hydraulic and some mechanical and other items to check on to be able to put in your truck.