HOW ABOUT A 1979 318 V-8 IN MY '73 SCAMP?

If you can’t witness the motor running, they should be considered cores that require a rebuild/tear down at the least.

What’s your budget for the engine swap? All this bouncing around your doing indicates you haven’t set a budget yet. Rebuilding a 340 is not as cheap as rebuilding a 318 or 360. While I hope it doesn’t happen, I could see you buying one of those 340’s only to realise the cost to rebuild it, drop in in your car and have it running will be more than your budget allows. Have you factored in a new transmission? A slant 6 904 transmission will not bolt onto a small block v8 block.

People don’t plan to fail but instead fail to plan.