66 Chevelle Chassis

[Dchv66]

Hi Chris,

After many years I've narrowed my choices down to Roadster Shops SPEC and Fast Track Chassis. Originally the car was going to be street/strip without much consideration for handling but that has changed since it will be driven mostly on the street. I have some concerns that need to be addressed before moving forward.
Engine is a Dart 555 BBC with fuel injection. Lemons Headers fabbed a set of custom Pro-Touring headers that fit within the frame rails of the stock chassis. I would like for these to fit within the new chassis but if they don't does RS offer custom headers for BBC applications?
Is oil pan selection crucial for custom headers? I'm pretty sure a kick out style pan may not work because it looks like a tight fit. The one my engine builder is suggesting is Moroso 21047 pan.
Transmission is a 4l80e, I'm assuming that floor pan modifications are necessary.
Comparing the two chassis it appears that there are two 9 inch housings. Can a Strange Ultra Fab 9 go in either ones place?
I'm interested in the floater option which may be only available on the Fast Track chassis? Looking at Baers floater rear brake kit for this spindle.

Thanks, Dave