Wondering if there is anything I need to change I know the iroc has a 3.23 rear end gear ratio and tbis usually have a 2.7x would I need to swap anything from the original iroc trans to the tbi trans to make speedo and everything else work right? Thanks

verify the rear gear ratio . then choose the speedo drive gear accordingly. you can swap the drive gears assuming you have two of the same transmissions

Cool thanks dont want to have to drop the trans twice thanks !!!

Not sure about automatics but the manuals are interchangeable. Even with the V6 manuals. The rear gear ratio of 2 something is for the automatics on the 305 TBI so I'm assuming you are referring to an automatic. I believe the automatics were the same as far as size and bolt pattern for all 3 V8 options (305 TBI 305 TPI 350TPI) the gear ratios might be different internally for each one but they should still be a direct fit. If you are going from an auto to auto I don't think you have to change anything. Might have to change that sensor. I am not very knowledgeable on this, but I'm basing this off of stuff I have read other more experienced people on here have been saying for years. I would double check maybe even Google it to see if there is anything that is different as far as making it driveable and working correctly.