I need the help of the exhaust system Gurus

[derotoreut]

I am getting ready to have a new exhaust system installed on my '69 C20, with 383 stroker, and I want to ask a few questions before I do it. When ready, I will be using the services of a custom installer.

1. What size exhaust should I run? I have a 383 stroker engine that was dyno tested at 465 HP/465 TQ. I am running Doug's D371Y Tri-Y full length headers, which have a collector size of 2-1/2". I am thinking of running the entire system in 2-1/2", plus using either "X" or "H" pipe (probably MagnaFlow mufflers). I want to make sure the exhaust pipe is properly sized.

2. Can I open up the rear crossmember to route the exhaust through it? My truck isn't lowered, but I think it would make for a cleaner install. I have seen some threads here where other members have done this, without putting any additional support structure on the crossmember. I don't really want to install one of the aftermarket ones if it's OK to open up the original. I just want to be sure I won't have a problem with the engine I'm running.

3. Is there a way I can route the exhaust in anticipating putting in a frame mounted gas tank at a later date? I don't want to tackle the gas tank issue now, but maybe sometime in the future. If there is some way I should route the exhaust, it would be good to know.