FE 390 what issues were there for this engine?

[RRRcobrasc281]

I just bought a 66 Fairlane GT but it didn't have an engine. The door tag states that it came with the 390 with C6 tranny. There is a guy local that is selling a 390 for a van with tranny attached.

1) Is there anything I should look out for or know about these 390 big block?

2) Are there any common mods I should know to improve this engine?

3) Dash pad is pretty much done. Didn't see one from Dearborn classics for the 66 and also the lens on the speed gauge was cracked and missing. Where to get?

4) has drum brakes up front. What car could I find to convert the fronts to disc on a budget?

5)And finally, I have a 91 Mustang GT donor with a tricked out 5.0L fuel injection motor when before the accident it could go down the 1/4 mile at 13 sec 105 mph. Should I just transplant it to the fairlane? Wireing is not a problem for me since I've already transplanted a 2004 Mach1 4.6L DOHC motor to my FFR AC Cobra replica.

Thanks in advance to all who can shed some light on this.