[OldCreek]

I used a 87+ tbi 25gallon tank in my 71 Blazer with 4" spring lift. It sits just behind/above the differential. I moved the rearmost cross member back to the end of the frame rails. The aftermarket tanks have a "baffle"...but it is just a really shallow reservoir. The OEM tanks have the full baffling...unless I just bought the wrong brand.

The fuel pump is another story. You'll have to get an intank fuel pump rated for the LSx motor. It should fit in the stock position/tank. I THINK I used an ACDELCO EP381 with a corvette regulator/filter WIX 33737.