New 64 Stepside. Where to start!? Help me spend my money

[tyler texas ranger]

Recently purchased a 64 and I'm mostly in love. Working on making it a daily driver/traveler with around $3000 immediate budget.


Specs:
Chevy 350
Muncie 4-speed /mechanical clutch
4.1 rear gears

The bad:
Transmission is bad (pops out of 3rd, grinds into 4th), no overdrive
8-10mpg
2600+ rpm on highway

The good:
Old tires and **** trans = burnouts all day.

Limitations:
I don't have a garage to do major swaps for engine/trans.
Know anyone someone in/around Austin, TX?

Prospects:
TKO-600 $2400

-price

LS engine $1000 +/- w/ trans $$$?

+reliability
+fuel efficiency

T5 Frankenstein transmission (camaro box/s10 tailhousing)

-time tracking parts
-durability

Any advice? I feel like a finless dolphin in a kiddie pool.