400 small block exhaust question

[milnesmcneil]

I have a 1977 scottsdale K20 4x4 with the 400 small block.

Would I have any problems installing a new 2.5 inch exhaust system using my original heat riser valve. I would like to keep the heat riser on the truck.

And what size exhaust system would you recommend 2.25 or 2.5.

Any recommendations would be greatly appreciated. Thanks for your time and help. Chuck