Just didn't want to by a 79 gas tube and stock.
Did buy the gas block.. Cut the 78's gas tube back 1 2/3" back, inleted the stock for the gas tube, inletted the stock farther back for the existing barrel band, and glass bedded the block to the stock (using plenty of release agent). Doubt it will shift or move, but will drill the two stock screws later this week...glassed in well, can remove the stock, but there certainly isn't any slack.
Worked. Once I get Photogucket to accept pictures again, will post one.
Basically have a long stock, long gas tube, QB79.