I was wondering what the differences are. I bought a gsr water pump thinking it would go on my ls (b18a) and I thought it would work.

b18a came in the 90-93 tegs and the b18b came in the 94-01 tegs. Power is pretty much the same. I believe that the b18b has a lil bit more power, but not much...

I know those basics but I am talking about physical differences. I thought I read somewhere that the gsr water pump will work for the b18 non vtec but wonder if it only works on the b18b opposed to the b18a.

that kinda depends...like the gsr water pump is 22 teeth as oppose to the LS which is 18 Teeth I believe...the reason the vtec water pumps have more teeth is so they can move water when they rev high up... if you start to spin a ls motor up to around 8K or higher...the pump is spinning so fast that it cant move coolant, and just cavitates. thats y when you do a ls/vtec that you get a vtec water pump.

The only way that you can use a gsr water pump is if you use a vtec timing belt

I know that as well and have a vtec timing belt but the gsr pump will not bolt to the block. Maybe what I need is a b16 water pump and timing belt.

that could be...i know the type r water pump should bolt up

Type R, B16, And GSR water pumps are all the same when it comes to the bolt paterns. It should bolt up no problems. Make sure that is the water pump you have, it should have 22T stamped on the gear and your stock LS should have 19T stamped on it. The only difference in the pumps is in the oil pumps. For a Type R the groove that the timing cover seals to is a different shape but it still wouldn't hinder the bolt patern to the block. Thats the case with the one I have anyway.