I cant remember the mm sizes but I run a modern freehub wheel + 8sp cassette on an 80s steel frame (originally 5sp freewheel). It takes a bit of huffing and puffing but fits OK in the end. I've not tried cold setting the frame. Note that I don't have clearance to use the little sprocket, so it's effectively 7sp. You may encounter similar problems.
Track bikes are 120mm, up to 7-speed 126mm, semi-modern cassette bikes 130mm and MTB 135mm. New road bikes also come with 135 clearance and some mountainbikes are 142mm. Downhill bikes are 150mm.
Life becomes so much easier once you've just bent your frame to 130mm and re-aligned the dropouts with a big spanner as Adrian suggested. The latter operation is important because an out-of-parallel dropout puts stress on the axle and bearings in the hub. This operation is so easy, it is jaw-dropping You literally grip the frame in your two hands and pull. Measure between pulls and don't be shy to push back again. It is as soft as cheese.
An aluminium frame on the other hand requires some serious force. A car scissor jack is ideal. You have to bend it way beyond the end point - so much so that when you do it people run away and dogs hide. You never show the owner of the frame how this is done. It is like a dentist pulling a child's tooth. Mommy must not see.
