Well I have a 85' S10 Blazer. Has the 2.8L engine. The thing runs, but is just filled with a ton of problems and the thing is just sludged to hell.

I am thinking that it wouldn't cost me that much more to do an engine swap, and would even be better for me in the long run. I am thinking of either a 4.3L or a 4.8L Vortec. Both of these engines can be had for super cheap with everything + tranny for roughly $1,000 with 55,000 miles or less on it.

Now, the only question that I have is will the engine fit and how easy? Do they both require a lot of modifications or do they slip right in for the most part?

 

While your at it go for a V8 , they fit in qiute nice but a tranny swap will aslo be needed ...
S/M Chevy's and Turbo 350's are a dime a dozen these days !
2WD or 4WD ?

My 85 :

 

DUDE!!! That is insane! 550hp?


Mine is a 4WD Blazer. I knew that I would need a new transmission. I would love a manual, but I think for this an Automatic would be better.
Though, would I also need a new transfer case and/or a front shorter/longer driveshaft?

 

If you go with the 4.3L v6 or any of the v8s, you will need the transmission from behind a 90* V engine. I believe that they all were the same so long as you get a 4wd 700R4 (4L60 non-E) so you shouldn't have any problems with your current transfer case or driveshafts.

The difference in work between a 4.3L v6 and one of the v8s is in the exhaust/oil pan/cooling side of things. The exhaust shouldn't be all that bad. There are oil pans available or you can modify one. The cooling shouldn't be that big of a problem either. You may need/want a larger radiator even for the 4.3L.

Check out JagsThatRun.com. They literally wrote the book on s-series v8 swaps.

 

Last question that I can think of. What about diesels? Are there any diesels that will fit in there without needing to also upgrade the front suspension for the added weight.

 

That is probably going to be quite difficult... Difficult == $$$. You could possibly mate up a small isuzu diesel to the transmission with an adapter plate, but then I would be concerned with the transmission taking the torque. Also, you would definitely need to regear the rear end and I'm not sure that the gears are available. Because most diesel engines do not exceed 2500RPM, you would need gears to be half as tall as they are now... A lot changes when you start talking about diesel engines... Not just the weight.