i got a 5.7 y pipe from a iroc would it fit 89 305 was about to put 3 in cat back exhuast with high flow car and woundering if 5.7 y pipe bolt up to my exhuast manifold my y pipe looks like its 2in or 2.5in and the 5.7 looks like a 2.5in maybe 3in outlet ?

 

From Transam350GTA:

There were only 2 different manifolds for the V8's throughout the years, but they were different depending on what motor and gearing package they came on. Here is the breakdown.

2" outlet manifolds with single 2 1/4" y-pipe
82-87 305 LG4 (VIN H)
88-92 305 L03 (VIN E)
82-83 305 Crossfire
90-92 305 LB9 w/o G92 axle (VIN F)

2 1/4" outlet manifolds with single 3" y-pipe
83-86 305 L69 (VIN G)
85-89 305 LB9 (VIN F)
88 350 L98 (VIN 8)
89 350 L98 w/o G92 axle (VIN 8)

2 1/4" outlet manifolds with dual 2 1/4" cats
89 350 L98 w/G92 axle (VIN 8)
90-92 350 L98 (VIN 8)
89 305 LB9 w/G92 Axle (VIN F)
90-92 305 LB9 w/G92 (Vin F)

JamesC

 

If you also got the exhaust manifolds from the IROC it will bolt right on.

 

yep. DO THAT.

Change the manifolds and y-pipe to the IROC pieces and you should have a drive-able difference!