You may just be pleasantly surprised what bumping initial timing,lighter advance springs and fine tuning your existing carb can give you! Not totally free but very Cheep......!
biggest problem with SBC that old is timing set and cam lobes worn out, not easy to fix but probably 30 hp increae from just replacing with stock parts, needless to say more hp with upgraded parts
I started with the low buck approach as a teen. Dual exhaust really helped the V8 vehicles. No emission stuff here and No need for a catalytic converter. Definitely a quicker advance curve in the distributor. Buy a recurve kit for HEI. like this one. https://www.summitracing.com/parts/...MI_5awpdHc6QIVisDACh1bags7EAQYASABEgJ0ovD_BwE I use the stock GM parts and only use the springs in the kits to recurve my distributors. If you are handy you could port your heads and pick up 30-40 HP. There is this and other books showing you how. https://www.amazon.com/Chevrolet-Small-Block-Cylinder-Motorbooks-Workshop/dp/0879385472 My first set was on a 350 Oldsmobile I had minimal tools to do the job. I built a valve spring compressor from angle iron I got from a bed frame someone tossed. For the porting I had 1 hard stone and a corded black and decker drill. Some valve lapping compound and wd 40. I started the job at 5 pm and car was back together by 1 AM. I was racing a buddy often and we were even every time. With the head porting I beat him by 4 car lengths and I was hooked on porting heads . A stone like this one on the left was used . https://www.harborfreight.com/5-piece-1-4-quarter-inch-shank-mounted-stone-set-94992.html
Well I will give you my best budget combo I have ever used in a long time. It's a Vortec 350 that I got as a core at the dealer I worked on. It pulls to 6500 and just screams. 350 Vortec std. bore 906 Vortec heads (all stock) LT4 Hot Cam with the LT4 springs and retainers. Vortec RPM Performer Air Gap 600 Holley, 750 Holley and a 600 Eddy was the best when it has no driveability problems 1 5/8" cheapo headers And not much more than that. Paid $50 for the core as it does have lower oil pressure but only has 8K on it. I hate to mess with it as it goes very well and gets great fuel mileage. I used to build a lot of 350's back in the 70's and 80's but the Vortec engine out pulls and outshines all the other SBC street engine I have ever used.
Assuming the engine is in good shape, the Comp Cams XE274 cam, Performer RPM intake, Holley Street Avenger 670cfm, headers and true dual exhaust will make it a different car, look at Comp Cams CamQuest for an estimate of the power increase! I have a '79 Z/28 with all of these modifications, see Youtube link below;
l put a set of Vortec 906 head on my 80 Z28 stock 350 with Edelbrock dual plane using original quadrajet carb. The heads increase compression by almost a point using a .015 shim head gasket. The mods really woke up the motor.
as previously mentioned.... You can dramatically change how the car FEELS and runs with some of the simplest things. While you may not be MAKING a big HP change....unleashing the HP thats already there will certainly improve the driving characteristics of the car. On an OLD iron motor....i really would NOT go inside of it without rebuilding everything. Headers and EXHAUST true duals Timing curve kit either a good CLUTCH FAN or electric fan Tune the carb....YES the ancient Q-Jet can perform just as well as any other carb !!! its already on there...per SMOG specs...so a little tuning can make a BIG difference. BTW carb and timing go hand in hand....you can't just touch 1 ....they are dependent on each other. Tranny shift kit https://quadrajetparts.com/rochester-quadrajet-c-128.html https://transgo.com/category/shift-kits/
no....that motor should be a LT1 motor...fuel injected computer controlled....thats an entirely different animal. However... the same PRINCIPLES do apply fuel curve, timing, breathing!