My 76's front end sit's up a little high for me . Is it a major ordeal to pull the springs out and cut them and re-install ? I have never done it . The Nova rides like a truck ,very stiff! I eventually want coil overs in the front. The engine is a 72 454 .
Riding high with a BBC installed means somebody has installed a heavier spring in place of the stock spring (probably a heavier gauge wire with a taller relaxed height having a stiffer spring rate or all of the above). Yes you can replace the spring easily enough if you are careful because there is a lot of energy stored in the spring.
Another thought is when they swapped springs did they put in polyurethane bushings? They are very stiff and without grease can act like extra stiff shock absorbers that will make for a rougher ride as well.
The springs if cut will make the remainder of the spring stiffer (as it will be compressed more and the spring rate (lbs./inch of compression) remains constant. A custom spring can be wound for your car if you do not mind waiting up to three months for the vendor (Moog and Eaton do this for their customers) to use the diameter wire you need (sooner if that gauge wire is used a lot). You need to find a friend with a four corner scale (roundy-rounders usually have this tool in their arsenal of chassis set-up equipment) to determine the number of pounds are on each wheel, and then you get to pick what you want the ride height to be.
Coil Over Shocks generally do not work with stock GM upper and lower control arms. That implies you are planning on changing more than just your springs; but are instead looking at an all new front end (possibly sub frame as well?).
II would find out if someone installed the wrong coil springs first, and fix it so that you will have a basis to build on for your new front end. Yes gas shocks will aggravate your ride height problem as a fully charged shock will be adding upwards of seventy-five pounds of up load to the chassis on each corner.
If your looking for inexpensive alternatives and you are worried that SBC springs may be a little to light you could always look into a set of Firebird springs. The Pontiac 350 to 455 generally all weight of these Pontiac engines change very little since the outer block dimensions stay pretty much the same and the Pontiac engine weighs more than a SBC and less than a BBC. If the Firebird spring gives you the stance you want you can always add Nascar style spring rubbers to stiffen them up and change the ride quality.