Jim, I think you mean 1.6, that's the only Sonic Mod I've got stuff from.
It was a project that unfortunately didn't get very far before it was abandoned, so there isn't much at all to it... also, a majority of it was rather poorly done.
I can give you some block suggestions from what was done in it though. For flipblocks, use a lo-res version of the tipping blocks from Chemical Plant Zone in Sonic 2. For breakable blocks, use the pipe caps from the same place. Powerup blocks could be a simple edit from the containers in the Sonic games. Just make the underside look like the visible weakpoint instead of the top and sides.
Not too sure what to do for enemies though. Do you think the armadillo enemy from Sonic 1 would work for one of the shelled enemies?
As for mode objects, coins would obviously be rings. Yoshi's Eggs could be Chaos Emeralds and the yoshis could be pedastals for them or something. The Sonic Mod used Robotnik, but that's just silly, especially if you decide to make a Robotnik skin.
As for powerups, the only somewhat decent changes were the 1up and Poison Mushroom, which were just Sonic and Robotnik's heads, and they really just looked weird.
You could probably use something like the leaping fireballs from that Marble whatever Zone in Sonic 1 for the podobo. (Keep wanting to type Marble Madness.)
As for skins, feel free to use my Sonic Battle skins if you want. They didn't look too bad, and I'd be happy to see them put to use for a change.