Just get some 14ga rectulanger steel tubing, cut it to run across the front and rear seat mounts, drill some holes and get some longer bolts. Be sure to use grade 5, or grade 8 bolts. You can paint the tubing black and get some of those plastic end caps for it. That would be stronger than a block under each bolt, and you can make it yourself for not a whole lotta $$. You can get the tubing at your local metal supply, Home Depot or, online.

 

Are u sure that it is not the seat padding that has compressed....1st gen carmaros are not made for tall people...or at least the ave height of our genertation at the time was shorter.
The other factor is the stop pad for the back of the seat has compressed or gone.

If NEED to raise like above post, longer mounting bolts and start by raising the rear mounts 1st. an over sized nut makes a great spacer.
you may also need to adjust back of the seat stop if it is new condition.

 

You may have a problem with the front bolts as they are on a vertical plane rather than horizontal plane for the rear bolts.
You would have to 'engineer' a 1/4 inch thick plate for the front bolts, drill holes, and through bolt the seat to the plate and use a longer length bolt for the bottom of the plate.
Then again, you might be able to unbolt the seat from the frame and add spacers there and use longer bolts. Probably the easiest method, you would have to check.

 

My wife is 4'11" and in a different car I had to make blocks to raise the passenger seat so she could see over the dash. I went to a fabrication shop and had them cut me 4 pieces of 2x2" solid aluminum square stock 1.5" thick. I then drilled a through hole, mounted with grade 8 bolts between the seat rail and the floor. I would pull your seat out and look at whether you want to add a spacer between floor and seat rail or between seat rail and the seat itself.

Steptoe is correct that the foam and springs in the OE seats compress and sag over time. My original seats sat almost 2" lower than a rebuilt set of stock seats. Not as inexpensive as spacers but worth checking out.

 

I had mine reupholstered with new replacement foam cushions from one of our vendors.
I'm 5.8" and now my head almost rubs the headliner.
Guess it does not matter anymore though.
I'm swapping out to 4th Gen Camaro seats now.

 

If you're going to drive it a lot, don't waste too much time with the stock seats. Save up (or cash out if you've got it now) for the Procar Rally seats. They have three different height settings, recline, and fit a medium frame person great. Mine are on the lowest setting and at 5'-8" my head is fairly close to the roof.

Seats and direct fit mounting brackets run about $800 for the pair and the matching rear seat cover is about $95.

 

I like the Procar seats also, but they don't make them in houndstooth

 

You can get them bare (ie: uncovered) and have an upholstery shop cover them.

 

If you're going to drive it a lot, don't waste too much time with the stock seats.

Yeap, American car designers could not design car seats back then..a bucket seat, a bench with a bit sliced out of the middle..shocking design.
I have stored mine away..(orginal upholstory new padding) and put 1988 Suburu leone/Omega seats in on the orginal runners and adapter plates front and rear made out of 5mm bar holes tapped in it.
They are the same diamentions, very comfortable, lean forward further for better access to the rear and also lay flat if needed.
Since the seats are from a right hook NZ car in a left hook camaro, it is the passenger who gets the seat with height adjustment also.