butt weld. Make sure your seams are tight, as even small gaps can make for an easy blow-through. As stated make sure you just get good tacks and skip around, as not to get too much heat in the pannel so it won't warp. Do a bunch skipping around, take a break to let it cool, then continue doing this untill you have a continous weld made up of tack welds.
My Father does upholstery, and the stuff he uses comes in a 5 gallon bucket, and is sprayed on with a paint gun. It is a contact type cement, and is yellow. You can get the high strength 3M contact cement in a spray can at Home Depot. There are 3 or 4 strengths, get the stronger one. You have to spray both sides, let it dry, then stick them together.
I say go for it, if you can really get away with it for a year or two without crippling you financially. You could always go back to the 9-5 if it doesn't work out.
Take out the bumper skock, gas tank, and tail light panel, and get in there and hammer and dolly that baby back into shape, then weld all the holes shut. Or, as said before, cut it out, and weld in a new piece.
The 350 from the Blazer would be less expensive, and more straight forward, not to mention easier to wire. Either one would be fun in a Z car. You should decide if you want a carb or EFI. That will make the decision alot easier.
I read it like he believes all the running gear is all factory original.
"The engine serial number matches the body. It has a 5 speed transmission, and i have every reason to beleive that all running gear is factory."
I agree a 383 stroker swap would be sweet in that car.
I am very curious how this will work out! I want power windows at a minimum in my Z. Since my regulator on the passenger side is shot, if this works as slick as you say, I will be pulling some stanza power windows mfrom the local yard!