i am swapping a 305 from a 89 iroc and a 700r4 from a 89 iroc into an 85 firebird and planning on rewiring the entire car and putting a hsr on it... are there any potential problems i might run into with the year of the motor and trans, or the camaro to firebird switch, the fitment of the hsr wiring harness or sensors, or anything out of the ordinary besides new brake line routing? i know i need a new tach, v8 front suspension, new accessories, etc. i just feel like its going to be alot more complicated than it should... any opinions are welcome

I know the 89 iroc will have a cable driven speedo so you will want to make sure your bird does too. You may run into a few snags splicing a camaro harness with a birds as a few things were different such as the rear turnsignals and such also the bird will have headlight motors to wire in. Overall it is not a super hard swap but it can be frustrating. If you run into issues look up wiring diagrams and if you still cant figure it out im sure somone on here has done it so the search will become your good friend

birds switched to vss before 'meros, in 87 iirc, deff by 89.

if its a 305 TPI car and you get the harness for that motor, the HSR will bolt right in no problems. You just need custom fuel lines made which is easy and not all that expensive ~100 bucks

good luck

thanks, wiring is more what i was worried about... eng and tranny are from an 89 camaro so they either both have the vss, or they both dont. if they do then i need to rewire the speedo right? ill update as progress/problems arise
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also i am getting the whole hsr kit with the computer and harness so i was wondering about that harness and fitment issues...

You dont need to get a harness with your hsr unless the one on the camaro is bad. The hsr is just fine on a stock tpi harness

When swapped a 3800II into my bird, the tranny was vss, but the 85 cluster is speedo cable. I had to get a vss cluster & rewire so it would work. If you can get teh camaro cluster , you might just need to do teh wiring.

edit: here's a pic showing the 85 speedo cable meets 88/89ish tranny

so turns out my trans is from an 89 formula, meaning its vss, and everything else is speedo, new gauge cluster etc etc. can i calculate the speedo gear i need and switch it in place of the vss on the trans?