You have one advantage, street and performance is close to you. They will have anything you need to put it in there. There are many ways to mount your engine. I'd start with a set of steel adapter plates for the LS1 like the ones you can buy on ebay. I'd then drop the engine into the truck and weld tabs from the stock mounts onto the new adapter plates so that you keep the stock transfer case location. Is there a crossmember under the oil pan on a 1988 4x4? My 92 4x2 had a truck pan on it and it worked fine. My 93 4x2 has a fbody pan on it and it fits fine. As for carbing a 1988 vehicle, better check with the DMV and make sure that's okay if Arkansas has any kind of inspections going on these days. I know Oklahoma quit inspecting vehicles all together.