Tim, those blanks were tough to come by when GUSA was up and running full tilt. My only recommendation would be to reach out to Billy Vivona (Billy40) on Noreast.com
or the NE Rod Builders
He was a GUSA rep and pushed the Mega/Monster Mag line hard and was even involved in having quite a few custom tapers made to his specs from Mag mandrels just for NY/NJ bight bottom fishing.
If you are looking for a great heavy bottom / chunking stick along the lines of the GUSA take a look at the Loomis / Rogue series of heavy bait rods for salmon fishing called bounce back rods. Eight foot 1pc very fast taper rods rated for up to 10 ounces . . . The heavy Loomis blank can be had for 119.97 from Hi's Tackle Box
with free shipping