the 188 ex is ok have used them in 600 engines you may see some hp with a1.900 but may not be that good to do with a stock head but they can be cut for them the 2.250 intake will work good but they may not be enough in the bowl to cut them out that big. i have cut gm heads in half you will have to watch this if you try to cut them way out. and work the bowl out you may have junk. 2.190 in and 188 ex will work fine try a set 11/32 stems if you what some more flow and help with mass what you need to ask is if i put the big valve in can i cut the the bowl out big enough to make the heads work better ?? you can put very big valves in but if you can not bowl them out much it will be bottle necked at the bowl so to be on the safe side 2.190 and1.88 with out seeing the heads