im in the process of swapping out my 4.3 tbi motor with a 350 also fuel injected throttle body. i am planning to use my current tranny, automatic 4spd with overdrive, i was told that it matches exact. i was also told my stock motor mounts would work without any modification. does anyone have any experience with this that could confirm these two things? i also need help with the wiring harness, i know i need the ecu from the donor motor, but i do not know which parts of the harness would need to come out as well
any help would be greatly appreciated

 

You will need the swap mounting flanges for the block. The motor mounts themselves will work, but the mount for the v8 swap is offset to put the block forward.

Check out JagsthatRun.com for more information on s-series v8 swaps. They literally wrote the book on it.

 

your trans does match but if you don't do something to upgrade it, it will be fried pretty fast. I helped i guy here in town do a 350 swap and his trans lasted all of a week. What was weird was as soon as he put the motor in it was sliping but didn't before i guess it was just weak but if you put a shift kit in and corvette servos you might be able to make it last for a little while. If you can get it to grab the gear then it oughta last for a little while.

 

You can use the motor mounts on the frame from the 4.3 and get the conversion mounts for them to bolt on the small block but the 2.8 frame mounts are a better option and more widely used. The biggest issue with 700R4 trannies after swaps is people don't adjust the TV cable properly and the tranny lasts a week very common.

 

could you explain that last part a little further?
and another thing ive heard is that the distributor cap will not clear the fire wall.. and also i will need a new oil pan to clear my front rear. i plan on doing a solid axle swap, and adding 6 inch coils. would that eliminate the need for the pricey oil pan if i do it all in one shot? and this leads to my next question, what axle is best for a sas?

 

Conversion Mounts - JagsThatRun.com
The brackets that are on your truck have the three bolt holes more or less centered on the motor mount instead of offset.

 

Improperly adjusted TV cables on 700R4's allow the tranny to shift at the wrong time allowing too much slippage and that burns up the clutches. When I did my swap I couldn't get my stock TV cable to adjust properly and needed to get one from an 89 fullsize truck to work proper.
If you have a 4wd you will need a conversion oilpan which isn't really that cheap or if you can weld you can make your own out of 2 pans