Incorrect Timing Adjustment causing heat issues?

If I had a small engine, and an automatic, and I wanted a lil more oomph off the line with my street car; then
the very first thing I would do is install a higher stall TC, without question I always put my 2800 in there. I have had that 2800 since 1978, and it followed me thru every smoggerteen I have ever owned. It is well worth the afternoon of work to get it up there.

BTW1
If I could get $600 for a couple of hours work. I would have to hang myself; I just couldn't live with myself; that is outrageous ....... unless it includes a complete re-bearing. and a SG tune-up..
BTW2
As to exhaust; A lo-po 273 automatic with 2.76 gears could push it's exhaust thru a straight straw to about 20 mph, in first gear at WOT. Ok that's a bit of an exaggeration, But as we have already seen, with a 2000 stall, the engine might be making 50hp gross down there, so maybe 43 net. For that, a single 1.88 pipe is already more than it needs.If you floor it at 33mph, so it goes down into first, the engine will buzz up to ~4000rpm, now at or near peak power, which IIRC was 180gross when new, so say 160 net, and now over 50 years later, maybe 150hp net . that engine will not need much exhaust system to pass that amount of power, which is at sealevel! not 4300ft elevation. :(
But this is something you can easily test with a pressure gauge. Just Tee into the worst looking pipe somewhere convenient between the Y and the muffler,and run a hose up into the cab, plumbed to a very low, wide-sweep, pressure gauge. Now take it for a spin. I like to see less than 2psi for a performance car, but for yours 3.5 to 4psi under worst case, IMO, would be acceptable.
But if the Y has been hacked for duals, I would pressure test it also, cuz I have seen some crazy hack Y mods.