1mm oversized good? does it depend on how much porting is done. Enlighten me. I am ignorant in this field

im getting ready to mount my T70 on my starquest, but it has a v clamp style exhaust housin on it, any ideas on where i can get one for our cars, or do i have to have one custom made. i just got a 2.5 downpipe off of ebay and i have extra v clamp flanges. i guess i can hack the pipe and make it a v clamp style DP, but i was hoping to go 3" on my exhuast so that would defeat the purpose. any ideas or advice???

I need an O2 sensor mounting plate for the stock downpipe. I need one with the threads so that I can screw in my bosch sensor. Thanks

89 ECU $65 shipped SOLD   complete TBI includes intake,throttlebody,injectors.TPS fuel pressure regulator, basially the whole thing.Contains an 850 primary to work with hacked 1gmas I can put the stock one in if you wish.185 plus shipping. updated here   stock exhaust manifold no cracks $60 plus shipping It has the stock 12A on it. update $50 for 12a has shaft play but is a good core for a big 16G upgrade   ported, extrude honed, stress relieved, step removed and wrapped in that high heat wrap b