Stea and DennisM thanks for the info on gas lines. I will use the 3/8 lines. Joe there are 2 tanks available for the 81 Blazer a 25 gallon and a 31 gallon. Dimensions for the 31 gallon are 28 3/4 length X 28 1/8 width X 12 3/4 deep. Same dimensions for the 25 gallon but only 10 3/4 deep. I used the 31 gallon in my sub and it fit pretty good. I had to do surgery on a portion of the rear crossmember and I made my own straps. There is plenty of room for the tank between the AD frame rails and I would think there would be even more on your Apache. Weeds