Help troubleshooting problem with my 83 Caprice?

I'm trying to find the problem by fixing the cheaper things first, rather than spend a lot of money on diagnostics. Besides the o2 sensors and electronic system has been diabled and nowadays mech are helpless without their comps or chips to tell em what's going on. So are there any oldschool mechs out there that might know chevys inside out , that would help I'd be eternally grateful. I have rplaced the factory 305 with a rebuilt 305 with the new reinforced cams. The distributor is replaced by a nonelectronic HEI, the intake is an Edelbrock, with a 650 CFM 4barrel carb.Anyways my son who I built it for drove it on a real muddy and bumpy in the dark and according to him hit a bump real hard. When I got home acouple of days later It would'nt seem to run much faster than 15 to 20 mph. It was like the car that usually could fly had asthma. I hope to God it's not the transmission for it has the Th 700 R4. Someone suggested the evap can, or a vacuum leak in relation to it. I heard that although evap can almost never go out, that if the do, you will have about a 75 or more % power loss.My friend Charlie kept insisting that it was the cat converter. So with much struggling in the heat(AZ desert) we got it off, only to find that it had no platinum mesh in there. So I took it off because a friend wanted it, but had to cut off rear fitting from converter and had the pipe insert pounded well into it and spotwelded (shitty weld, but since I was broke I couldn't just pick my welder), I clamped everything in place, started her up just to find that it leaked right there, by placeing my hand near the weld. I should just have left the converter on as it had no obstruction. The car also keeps surging, so I suspect that the convertyers platinum mesh got blown backwards, and is now obstructing either the muffler or got caught in one of the many 90 degree agle turns on that tail pipe, making the leak at the spotweld even worse as that exhauxt is trying to take the path of less resistance prior to the obstruction. Could I be right in this umption? SO I went to dismount the blasted muffler only to find that it's not only clamped , but also has a ugly big weld job on the rear sise of it. I wanted to see if I could take the muffler off and look for or try to clear out possible obstruction, and while muffler was out run a semi rigid wire thru exhaust pipe both in front and towards the rear of muffler. Finding that weld was really dissappointing, as I now have no money to pay other, and live way out there in the desert with my 16 year old kid, and without wheel I can't even go get a job, nor anything else. I've been walking 14 miles to town in 100 plus degrees, to the junk yards to try to find parts. It's really hard as I have no money, nor anyone to help. And every time I think I've found someone to help, all they wanna do, is help themselves. I'm running out of time,as I can't be without electricity, and without work, can'e make money. Some one suggested that an exhaust leak can cause a vacuum leak. And the Transmission governer was mentioned. Please help anyone