Well, after a lot of work and trouble shooting it has come to my attention that my engine is shot. This will be the second time replacing the long block.
Any advice as to what I should put in there? I was thinking of an LS swap but am not sure of the difficulty and if it will run with the stock ECM?

Thanks for the advice

 

Forum member AgentEran installed a Golen engine. I don't see him here much any more, but you might try PM. Also searching Golen on this forum should give you other perspectives. Good luck.

 

The 1986 ECM is not capable of running an LS. Fortunately, you've got some really good options out there that will. The most cost effective option would be to get the PCM and harness from the vehicle you pull the engine from. Otherwise: the aftermarket has some real nice options out there.
I just finished swapping a turbocharged LQ4 (6.0) in place of the 350 that was in my Suburban and used a Holley Terminator X Max to run it. (Needed the Max to control the 4L60E that will be swapped for a 4L80E soon.) That is their more "entry level" system. I've got the HP in my 85 and have found the Terminator X to be absolutely fantastic despite being the cheaper system. (I'm entertaining switching to it when I LS swap the 85 so I can run a DBW throttle body.)
I will say that not only is the LQ4 more powerful than the mildly built SBC it replaced, it is also more efficient if I keep my foot off the loud pedal.

What are you looking for with your new engine power wise? If your'e looking for basically a stock replacement in a SBC (or something mildly built) I would try to find one of the L31s like I pulled from my Suburban. Late GMT400s had them. (For reference: my Suburban is a 99) They have 4 bolt mains and a one piece rear main seal.
If you want much more power and aren't afraid of doing some wiring I would suggest going LS. It's where I'm going on the next engine for the 85. (Planning on turbocharging one of the aluminum 5.3s.)