runing out of idea´s on what to improve

Define "reasonable cost" and it will help.
However, starting from the top of the engine;

A K&N or equal 4+ inch filter with extreme top.

If you like your Edelbrock carb, so be it. I'd do (At your level at least) a Holley DP. Your build so far is a stout one. :thumbrig:

The intake is very good. Only bested by the Mopar M-1 single plane. Theres a few mods that even help that one out. Contact DLI in Cali. U.S.A.

Your heads. Iron J heads limit your performance even now. IMO, I'd spend the cash for ethier the MoPar Large port Comando heads or the Magnum R/T's fully ported. CAreful with the Magnum heads since there rocker ratio is 1.6 and not 1.5.

Exhaust. Your tti are about the best you'll get. Then theres race headers. Enter the catch 22 of it all.
I do not like those mufflers, but that choice is a personal kind of thing. I myself would be looking at a set of Dyno Max ultera flow mufflers.

Not a auto tranny guy, but I think you need more stall.

Your 8-1/4 is going to explode soon. You'll need a 8-3/4 at a min. I know you said cheap, but this expense of purchasing a DANA is probably very worth your while.

All costs would be considered reasonable though expensive unless you wreck it before upgrading to the better parts like the rear. Then your replaceing the blown up rear and what ever other damage it causes.