I've finished building my kit from 1996 over the last few years.
One thing to watch is the motor mounts.
I'd have to see which side of the post your supports are to confirm. see attached for photos of two different vintage contemporary manuals.
https://imgur.com/gallery/elFZ1k1
I have a Howe Racing Enterprises, Inc. radiator that came with my kit, mounted vertically and I don't have any overheating issues. I do not know if they had different radiators for 351C vs 427 FE's .
You'll probably also have to watch the height that you cut your surge tank down to get it to clear the hood.
Another item to watch is the height of the carb relative to the hood scoop. I have a over bored 390 with Edelbrock Aluminum top end kit and I only had room for a 428 CG carb spacer on top of the intake.
I have a TKO 600 and went with a Tilton Hydraulic Throwout bearing due to the clutch fork angle on the stock quick time blow proof bell housing.
Also watch how you have your new headers and side pipes made to have decent ground clearance.
Good luck.
Mike