There is a HUGE difference between running the Baja 1000, and running it competatively. We're talking about the former, not the later. Mad Mike (perhaps you know him Sumo from your prorally 'experience' - he won national production championship few years back with stud bug) ran a stock D-50 pick-up in pro-rally for a while. Cage, some shocks, and a welded rear. Other than safety stuff, that was about it. I crewed for him a couple of times, helped stab his motor, mount the fuel cell (not required, but wanted), even raced it in a rallycross after rolling my truck. Anyway, he ran that truck with just the basic prep. for safety. Was he competative for overall wins? Hell no. Did the truck hold up well enough to finish rally's? When he didn't try wrapping it around a tree, ya', it did.
Don't look at prorally subaru's for comparison, look at individual competators. Used to be split into Club and Pro, but I haven't followed it in years. Club guys were average guys, in average cars (no 400hp AWD turbo's), running the rally at far slower rates. Used to be on a rally weekend, there were two club rallys, one each day/night and the prorally was basically both of those run together.
Class 11 beetles. They run basically stock except for a cage. And they finish - though I don't think they run the whole 1000 cause of a total lack of overall speed.
Can a 80 run the baja 1000, with a gas engine and auto tranny? YES. Can it make it the full 1000 miles? Certainly. Will it be competative? No. Don't think that's the goal here. As long as the red haze doesn't take over and he doesn't suddenly think he's Ivan Stuart, shouldn't be that big of a deal really. Safety stuff first. Then the best shocks you can afford, and fit for the class rules. Some tube bumpers, couple of spares, a long range tank, and go have fun. Other than protecting the engine from dust, don't modify it. You don't need any more power than what it provides to finish, and any more and you'll just push other parts beyond their limits. Heck, get a '91/'92 3F. That'll keep you slow enough to keep from braking stuff. That's part of the key to class 11 beetles, they don't have enough power to break stuff!
Just don't get in your mind that you have to keep up with that buggy in front of you, no 30ft jumps, keep a swift pace, yet one you can maintain for hours on end, and send us pictures from the finish line.