As I said in the PM you sent me, I'll answer your questions here so that others can also see it in the future. There are several threads on this that you can also read.
For starters, you need to have good fabrication skills or know someone who does for this swap, otherwise you'll probably get pretty frustrated.
The hardest part is definitely mounting the cab. Many people don't do the swap on these earlier trucks because the cab is narrowest at the point where the S-10 frame is widest, which can make things very challenging. This also makes it difficult to get the cab low enough on the frame, and get it far enough back to get the front wheels centered in the wheelwells.
On mine, I had to notch the back inside edge of the front fenders approximately 1/2" in order to get the clearance needed to put the cab in the right spot. The running boards went in fine and you can't tell at all this was done. This isn't possible with fiberglass fenders and running boards, if you're going that route you would need to modify them further. You could also modify the frame, but that was absolutely out of the question for me.
My cab is sitting roughly 4" off the frame, which gives me a box depth of 12" (because of the kick up of the s-10 frame in the rear), and also gives me a completely flat floor in the cab. I have 2" dropped spindles and 3" blocks on the frame, and this puts the bottom of the filler pan in the front at 6.5" from the ground. Since my truck is a GMC, the filler pan is a bit lower than on a Chevy. But I'm also running 27" tall tires in the front and 31" tall tires in the back, for the look and gearing I want.
The process we go through for these swaps (this is the 4th truck we've done this way, but the first art deco GM) is as follows:
Strip the S-10 frame, removing the motor (if not using the S-10 engine), all unnecessary brackets, etc. Get the brakes and steering in order, and change any axle seals, etc, while it's easy. Mount your engine and transmission, and find a driveshaft of suitable length. Your engine should be mounted wherever it needs to be to get the spacing right to the firewall, in order to get the firewall where it needs to be to space the wheels in the center of the wheelwells. It takes lots of thinking and measuring but is very crucial to get the right look and spacing. Get your fuel lines in order while they're easy to access, at least on the tank side and to the fuel pump. I left the carburetor off until after the cab and everything was mounted, but the engine was all built and painted otherwise.
Once the frame is ready and the cab is loose and ready from the old frame, you can begin to mount it. MAKE SURE YOU LEAVE THE FRONT END ON THE CAB WHEN YOU"RE SETTING IT ON THE FRAME. Many people make this mistake, and it's crucial to leave the front end on to make things as easy as possible. Once you have it mounted, you can take the front end off if you want. We use a skid steer loader to lower the cab on the frame, and you'll end up taking it on and off a dozen times or so before you set it on for good. Each time you'll mark where you need to clearance, taking little by little until everything fits as it should. Once you have the body set on the frame and everything clearanced, you can make the body mounts (2 in the back of cab, 2 in the front of cab, and 2 on the front end) and bolt the cab and front end down. My front cab mounts are the old cab mounts from the rear of the s-10 cab, cut to the right length and welded to the top of the frame.
Once you get the cab mounted, you can put the running boards and box on (with fenders) and mount it all at the same time, so that you get the right spacing and look on the truck. You will need to trim the frame rails at both the front and back of the frame to properly set the body down.
If you don't feel you'll be able to do all this and fabricate mounts, you shouldn't begin this swap without the guidance of someone who is comfortable with it. If you're comfortable with it, have fun!
I have some pictures, but nothing detailed enough to help you on your way. If I took all the pictures of the steps needed we wouldn't have had the body mounted on the frame in 5-6 hours.
