has anyone ever tried to install a set of 3rd gen iroc on a 1st gen?

http://d.im.craigslist.org/xL/ri/W6sKJNhyv9hARaUM077JvRELh8yk.jpg

Yes. They fit, front rear, rear on front, otherwise they drag the shock mount. I'll be putting some on '67 soon, I just need to get the correct lug nuts (the taper is unique to the 3rd gen wheels, and yes, you CAN just use the tapered parts store lugs, but it's unsafe and hard on the wheels!) I'm gonna look up the folks that make the correct lugs...or I suppose you could swap your lugs to metric and reuse the the stockers.

http://www.camaros.net/forums/showthread.php?t=72693&highlight=iroc+lug+nuts

read this one on the lugs.

Yes. They fit, front rear, rear on front.

is one set wider than the other - how would i tell the difference?

They are marked on the back, FRONT and REAR (I'm not being a smarta$$, sometimes it's different!) You may also have to watch if you have DIRECTIONAL TIRES, but it isn't a big deal, just check, for right and left as well.

Anyway, the backspace is different from front to rear.

try THIS thread too:
http://www.camaros.net/forums/showthread.php?t=33312

There are some differing opinions in there.

I can say on a '69 Camaro discs, Firebird drums, '73 drum and '74 Nova disc, front on rear and rear on front. I had problems with the rear dragging on the shock plate if installed how they are supposed to go. Narrower (225/60/R16) tires in the front solved any rubbing issues (I used 245/60's in the rear which drug if fully loaded, ie larger people in back seat and extreme turns combined)

On more note: this is my first time on a non-staggered shock (67) car, rears my work fine in back... '68-69 and multi leaf Novas I had issues with.

not totally the same, but i had IROC's on the Nova, and the rears went to the rear and the fronts to the front with no clearance issues except for a slight rubbing on the frame at full lock on the back side of the front tires.
oddly enough, when i got rid of them and got a set of GTA wheels with the same offsets, i had absolutely no clearance issues at all.