So I recently got a 1979 it 250 and I have been looking around for possible upgrades to the bike and I havent really found any. However, I know that DG made a pipe for the same year YZ. Because both of these bikes use the same cylinder will this fit? Also, will I see any power gains from it?

Here is the pipe/ exhaust if anyone is wondering. 
www.dgperformance.com/dg-performance-mod...979&prodType=Exhaust

If it fits then i'm sure it'll go better providing you buy their muffler for the end & don't use the IT original. I'm surprised the It uses the YZ cylinder & thought they'd be milder ported by a little. But yep, same part number. I see the head number is different but pick looks the same so wonder if its got a higher compression in the YZ head. IT shows two head gaskets so ditch one if yours still has two. I remember on later IT490's they came with a restrictor ahead of the carb in the rubber manifold--just a restrictive washer. Unlikely with yours i'm sure being a 250. I bought a DG overstock pipe & muffler for my YZ490K "83 about 10 years ago. Was a bad fit & had to heat & bend it to fit square on to the cylinder--side angled exhaust flange--DG just having a bad day i guess. but annoying at the time as cost the earth & bought for my specific model of bike. Yours looks a central port so hopefully no problems fitting.

www.partzilla.com/catalog/yamaha/motorcy...linder-head-cylinder
www.partzilla.com/catalog/yamaha/motorcy...linder-head-cylinder

Thanks for the response. I cant be the first one to have thought of this though.

Actually thinking again the IT frame would be a bit different in the rear subframe so hope nothing gets in the way of the pipe or muffler.