I just did an engine swap on a 76 Ranger high boy. I bought a good 390 engine from a local salvage yard with a 30 day warranty for $300 and it took me a couple days to install. This may be another option for you. I can do the work for you but I'm located up North by Loveland. I have a truck and trailer that could be used to bring the truck up. If you choose to buy a rebuilt motor I could help you do that also. I'll charge you less than what a shop would charge to do the work plus a tank of fuel to pick up the truck. Let me know if your interested.

Bill