FWIR, transfer tanks are only legal in OTR's.
If you do opt for a transfer tank then you need to watch your fuel guage to make sure that you do not overfill the primary or you'll have a serious fire possibility.
The GM 6-way valve is something like $50 It'll switch both the supply and return lines. Use a DPDT switch, one to control the valve and one to switch the sender. That seems simpler to me than a transfer pump coupled with not knowing how much fuel is in the Aux tank.
