S10 engine swap(2.5 to 4.3)

I am thinking about doing an engine swap with my 87 S10. It currently has a 2.5L 4 banger. I would much rather it have a 4.3L 6 cylinder. Correct me if I'm wrong, but if I bought a 4.3 from another S10 it would just bolt right in. I am wondering if the same, stock transmission would work, and if I would have to do any modifications. What all would this envolve? Also, would a 4.3 from a newer S10, like a '98 or even '02, work? Thanks in advance, any advice would be great.

changing out your 2.5 to a 4.3 should change over just fine as long as you change the motor mounts and computer ( 2.5 comp will not work ). you can also have the 2.5 bored if it has a manual fuel pump and have same tranny work done

Thanks. I'm a newbie, how complicated would it be to change motor mounts and computer?

the mounts on the engine aren't a problem but to change the comp you are going to need the engine compartment wiring harness

If I wanted to swap a 2.8 into it, would I still need to change the wiring harness? Thanks a lot for all the help.

ok.....if u went from a 2.5 to a 4.3, u would have to get a new tranny as well, they have entirely different bolt patterns the 4.3 has the same bolt pattern as a 350.....plus new comp. and wirin harness, but on the other hand a 2.8 will fit on the 2.5 transmission, but u would also have to have a new computer and wirin harnness

Since the 4.3 is heavier than the 2.8, would I get about the same performance out of each one? One more thing, how much worse is the gas mileage on a 4.3, than the 2.8.

Personally, i have an 89 S10 with the 4.3 4x4 backed by a factory 700R4 Tranny...and i get about 18mpg on a good day...but back when it was newer it got around 20...(so i am told)...oh and if you are going to hot rod it....it has one heck of a diet for fuel!

why would you need a new computer if you switched from 2.5 to 2.8 engine if they both have TBI??

my cousin did a 4.3 to 5.7 swap in his 89 and when they first fired it up it ran on the 4.3l computer, being tbi, but it ran like shit at anything over idel, the fuel curves must be different, you would need the 4.3's harness for the engin bay sorry, and if you got the newer one, you would also be goin up to obd2 as a computer, meaning you would need to upgrade the transmission to manual or a 4l60E transmission

anyone know how to do the wirng on a s15. I just recently did a conversion on my 84 gmc s15 2.8L. I switched it with a 89 s10 2.5 kept the v6 tranny and was wondering if anyone knew the wiring on them. thanks

Just my opinion, but for the money and time it would take, you are better off selling the truck and buying another with a 4.3 init already.