When I first purchased this vehicle, I had to repair the power windows, replace the turn signal combination switch, replace the convertible top, and replace the front right motor mount.
This vehicle requires a great deal of work, however I am a GM Line Tech, and I am also an ASE Master Certified Tech with nearly 38 years experience, and I will have no trouble returning this vehicle to pristine condition.
I am spoiled with 1990 to 2000 W Body vehicles, and will never own any other automobiles!
Personally I prefer the 3.1 V/6, but performance wise the 3.4 V/6 will run like a raped ape!
Just for FYI, the 3.4 V/6 is in actuality a 3.1 V/6 lower end with 3.4 dual overhead cam heads.
Yes the block casting is physically the same, but is machined differently.
However be sure to get a 3.1 motor with both the front and rear exhaust manifolds, and the front to year exhaust connector pipe. You will also need all of the bolt on accessories, alt, PS pump with at least the PS high pressure hose, A/C compressor and the A/C hose assembly for the 3.1 V/6, belt tensioner, and water pump pulley and serpentine belt. You will also need the upper and lower radiator hoses; the radiator will work on both the 3.1 or the 3.4 engines.
To replace a 3.4 V/6, with a 3.1 V/6, you will need the 3.1 V/6 motor mounts including the dual upper dog bones, the ones that connect at the upper radiator mounting brackets.
The wiring harness is the same, only with different harness configuration because of the larger 3.4 V/6.
It is best to change the wiring harness with the harness out of the 3.1 V/6, replace it from the firewall out.
If you're experienced enough, you can change the 3.4 harness to fit the 3.1 V/6. However, if you're going to use the 3.4 V/6 harness on a 3.1 V/6, then you must reconfigure the 3.4 V/6 wiring harness properly; make sure and use the metal insides of the red but connectors, make the crimps are tight, then insulate the connections with shrink tube, and protect them in the black plastic wiring conduit. This will also make the harness look factory.
If you don't do this, you will create many electrical connection problems, and if you live in a northern states where salt is used on the highway, then you will not like yourself after one (1) winter season; you will have electrical connector corrosion problems beyond belief!
Make sure and check your cooling fan(s) operation before you take your car out for a test drive after you're done.
If your cooling fans are not working properly, you're asking for trouble.
The left fan will only work after the motor gets above 220 degrees, and the right fan will only work if the motor is very hot, or when the A/C high side pressure is above 300 lbs!
So! Boys have fun! It's a lot of hard work, but it's worth it, and it can be done!
Any questions, feel free to call
Steve @ 321 206-8910
No charge for advice!!!