i just changed over to stainless marine crossover from a circ pump but my thermostat wont fit into the new housing, should i run one at all

Varied ideas/opinions on this one, I feel a Tsat should always be used. You need temp to help to get rid of the condesation in the engine and to bring the metal parts up to tolerance, most raw setups can use a 140 I prefer a 160.

I agree, SM has a t-stat housing also with a t-stat and bypass holes , I used these in my 29 fountain with blower motors and loved them.

shouldn't the stat fit in the intake?

Duh! Glad some one is thinking!