1980 Performance

[jccatwb]

I have a new -to-me 1980 Avanti with a 350cid sbc, TH400 trans, and type44 (3.07) differential. It does not perform as well as my old 63 R2 with power-shift and a 3:73 diff.  The exhaust system is a mess But is functional so it will wait. What have some of you all done to make these strangled engines perform a bit better?  (On a budget!)  (The meadow burner is thankfully gone as well as smog pump and all that crap. )  Best timing?   Thanks in advance!