Jasper offers cleanly done rebuilt engines, but in stock trim for the most part. Back in the day, they did nice 7M-GTE remain shortblocks and longblocks and typically did the machining well enough that you could just install an MHG without any fuss. Toward the end, I believe they offered a metal headgasket and ARP studs, but that was the extent of their upgrades.
Jasper offers a lot of different HP levels in things like SBC, SBF, etc rebuilds, but not for 7M-GE's and I'd honestly be shocked if they even still offered a 7M rebuild. There's so much required to pick up 50hp on a GE, that your friend is simply full of shit and/or confusing Jasper's options for V8's that are easy to bump HP on with milled heads, etc.
A very good friend of mine is the regional rep here for Jasper and he personally owns a nicely built 7M-GTE MK3, and we have never spoken about 7M builds by Jasper unless it's a quip about 'back in the day'.
So yeah, all in all, I wouldn't sweat it or spend the $3k on one even if it was available. $3k will go a long way toward a JZ swap though, and that's a much, much better option!