Welcome to StangNet!
Okay, here's the priority list:
1.)
BRAKES BRAKES BRAKES! Before you worry about improving the speed, improve the stop - but you already knew that. Brakes aren't "rocket science". Unless you've had strictly
newer cars for the last 20 years; drum brakes aren't unheard of in your world.
Front drums might be a little more interesting.... unless your car has hubs separate from the drums, you're looking at checking out/re-packing the front wheel bearings when you do the brake job. No worries; I've done that on front disk brake cars (specifically, my '73 Gran Torino); as it had integral hubs and rotorsjust like some front-drum-brake cars.
2.) Tires! Once you have the weedy, wimpy tires replaced; you can start looking at the steering issues. Needless to say, the car will handle better if it's
not having a blowout on the road
3.) Transmission. You said the engine has "25 HP". If most of the engine's power is going away with the tranny slipping, you're thinking the engine's a wimp because most of the fluid that gets the power from the 302 to the wheels has dumped all over your garage floor! A new pan gasket and fliud filter (it's 'just a piece of window screen') are replaced, most of the fluid should stay in the transmission. Other possible places for it to leak are the transmission's rear seal, just like the engine's rear main seal can fail and dump oil all over the concrete - except it's somewhat easier to replace; also around the shifter shaft (the part that hooks to your shifter and tells the tranny what gear you want it to be in); or around the front pump. I just ran off the most likely places for a leak in increasing order of "PITA to fix".
3.) After these three, I'd deal with the steering/
suspension first, then any engine issues. I don't know what your level of competance is in auto mechanics.... I personally had a Dad who made me learn how to do maintenance/repair before I could get my driver's license; because "I don't wanna hear that you're stuck in the middle of Billy-Blue H*ll because you didn't know how to fix something stupid!"
Add in the fact that I couldn't afford a vehicle with less than 74,000 hard miles on the clock until I was 30; and you can figure out that I spent a bit of time on the side of the road "...in the middle of Billy-Blue H*ll..." learning how to get the car/truck going again.
(The locked-up rear (drum) brake on my Torino was a perfect example).
If you're unsure of anything (and even if you aren't); first things first
GET A REPAIR MANUAL! Either a factory-spec manual or even a Chilton's/Haynes manual is better than nothing. Second - there are about 1000 guys on here and/or over on the "Classics Tech" forum who probably experienced everything you are experiencing or have broken everything you're probably gonna break - ask questions, use the "Forum Search" button.
Above all - relax! A '65 Stang is more basic (read: "Easier to understand and fix") than even your '73 Vette. It will be okay!
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