Gas tank - Under-bed or behind-seat?

[DarkFlounder]

The PO of my '72 had removed the original tank and installed a driver-side saddle tank.

I'm getting my replacement bed ready, and I want to replace the tank. So, my options are an under-bed side-fill tank (I'll probably put the filler in the left-side of the bed), or take it back to original.

It's too late to take the truck back to original, so I'm looking at purely convenience, ease of install, and usefulness. The PO put sub-woofers behind the seat, but losing them is not a deal-breaker.

I've also given thought to putting a bigger tank under the bed, maybe a 31gal Blazer tank. It's a long-bed 4" lift 4x4, so under-truck clearance isn't so much of an issue.

Opinions?