Honestly, there's really no telling what the heck were in those extracts. Having never used any of them, this is just a WAG, but I'd just increase your specialty malts by a bit (maybe 50%???), and use enough Pale Ale malt as a base malt to hit the OG you're targeting. For an imperial stout I'd bitter to 60ish IBU's at 60 minutes with whatever bittering hop you have on hand (Magnum, Nugget, Galena, CTZ, Apollo, etc.).
FWIW, I think Coopers makes the hopped extracts in Mr Beer Kits now. If you can find a few stout kits that may be worth subbing in to go full retro on this.