I have a 1978 Z-28 with a 350, standard, and a low geared rear end.
I Dyno'd it last year, I got 151HP and 238 Torque at 7000 ft elevaton.
I'm interested in upgrades to do to hit the 300HP mark.
I don't have a ton of money to put into the car, but I'm ready to hear your suggestions.

 

Sounds like its tired .But you could do the normal hot rod stuff as you can afford it, like an intake ..headers and true dual exhaust .a cold air box there are different ways to do so Look at the 1960 and early 1970 muscle cars for ideas.and a good tune up as well I started out that way with mine .And just added to its as time and money and life permit.Good luck to you .

 

Where the heck did you dyno at 7000 ft elevation? That's pretty high up!
The air gets thin at higher elevations so that doesn't help any for making horsepower.
The problem with motors of that vintage is that they were low compression,that limits what you can do short of a rebuild with better pistons but you can still do the basic package.
That typically consists of headers and better exhaust, a better cam with an intake and carb upgrade.
That's about all you can do not having much to spend and even that will not be cheap,it might get you near your 300hp mark if your motor is in decent condition.
The first thing I'd do is a compression test to be sure you have a motor good enough to work with.
Right now is a good time to buy used speed parts for small block Chevys with so many going LS power there's tons of stuff on eBay,craigslist and at swap meets etc.
You might find a good intake and carb or even headers used but it's always buyer beware when you get used stuff.
I'd steer you towards one of the proven package deals from Edlebrock or the like.
Something like this along with headers will give you a good bump.... https://www.jegs.com/i/Edelbrock/350...hoCHTcQAvD_BwE

 

Nitrous injection.

 

300 is not that difficult... In the early 80's, we bolted on a set of 56cc chamber heads, put in a cam, headers and a new 4bbl holley or preferably an AFB... instant 330 hp.. Nowdays, you can buy everything aftermarket, and don't need to worry about upgrading the valves and guides in an old set of heads. My 80 is/was probably more lethargic than your 78, and even had an 80mph speedo, but the blower instantly jumped it to over 300hp... while I wait for the 434 from White performance to arrive :P

https://www.jegs.com/p/Edelbrock/Ede...60264/10002/-1

 

That'll fatten up that thin air!

 

I have formula. How far are you willing to go? And how far is your transmission willing to go?
Is this a daily driver?
And do you have a budget?
Anything else you could tell me about the car?
Is it a stock deck block?
You need boost at that elevation in my honest opinion. A small supercharger or turbo. Although if your not willing we can still accomplish it naturally aspirated , in this case I can build you an engine. It shall be a 391 small block from a 350. its a 350 with an offset ground crank for use with stock deck height 350 block. And it shall get the job done.