Join Date: Jun 2004
Location: Northern Nevada
I'd be reluctant to spread those dropouts, but that may just be my natural distrust of alumuminum--I don't KNOW that it would cause trouble. I've spread steel frames from 126 to 130 a couple of times with no trouble.
There's no need to change shifters unless you can't use a friction setup. My two main road bikes, an Atlantis and Rambouillet, both use barcons in friction mode (8 spd on the Atlantis, 9 on the Rambo) and shift fine. Indexing is overvalued, IMO--I'm not anti, but for everyday riding, the advantages are tiny if they exist at all.
If you switch, you will need a new chain, though. I'm almost certain the 7sp chain is wider and won't work. SRAM chains are modestly priced and work great on my bike, plus you don't have to screw around with that Shimano pin.
Others may disagree, but at least for me, this swap wouldn't be worth the cost. Until recently I had a 7-speed Allez, too, and it didn't give up much compared to the eight and nine on my other bikes. But your choice, of course.