Re: '68 Father and son project..
Are you sure the radiator inlet/outlets are oriented correctly? Most chevys are the exact opposite of Fords orientation. Also, the width is against you. It will probably hit the battery tray. Might look into relocating the battery, or changing the orientation of the tray with a tray from a '67 Mustang.
Know that the Fairlane floor pan is a bit of a challenge to mount buckets to. It's no where close to flat (unlike a Mustang). The challenging point if the mount for the rear, inside bolt - with the factory floor pans, it's just left hanging in the air. The factory used stamped metal spacers that the mounting bolt would run through to support this corner of the seat. Bench seats did not require any support in this area.
When I installed Acura seats in my Ranchero, I used seat brackets from Corbeau, which fit the floor reasonably well. Still had to mount them to the seat though.
'68 Ranchero 500
'70 Cougar XR-7 Convertible
'98 Mustang GT Convertible