Carl,
You are asking about the carbine model I believe which has the 18-1/2" barrels. Rem brought these out for about the last three or four years that they made the rifle. There is no difference between the carbine and regular model except for the length of the barrel. Also the carbine and last models of the 788 had a straight comb versus the monte carlo comb of earlier rifles.
I have two of the 788s, one is a 6mm that I bought in '76 and a 22-250 that I bought last year. I will never sell either as I love both of them, both are more accurate than I can shoot them. I feel they are an excellent rifle but the prices are getting high on them now.