Hi Ami,
Just seen your post on this subject and it reminded me that you asked this question at the Sussex Club meeting. Good to meet you there - that's a lovely car you have and it has some interesting and really nicely done mods.
This should work for your '79 as well as the 68-76 as shown here. I think the actual cushion design changed in '78 but the basic frame stayed the same.
To answer your question - the seats do have some adjustment for recline although they are not quite as easy to adjust as they might be.
There are 4 large headed bolts that control the recline angle - two are fitted to the back of the seat squab frame and 2 are fitted to the bottom of the back rest (see pics of my rather ratty seat). They should be clear to see if you pull the seat backrest fully forward.
here's one on the seat base... and secondly all four
View attachment 24343 View attachment 24344
Unscrewing the bolts on the bottom of the seat back (or screwing them in) changes the recline angle - just make sure to do the same amount on both sides or else it will twist the frame.
I found a video regarding this on You Tube...
76 Corvette Recline adjust
.... which shows it very well. Incidentally this is quite a good channel for later C3 info and 'how-to's'
Whether this will be enough for you depends on how far these bolts have been adjusted already but it's worth a try before considering an expensive swap option.
Hope this helps.