455,
Check to see what jets & slide # is in there, as you can have the 38 bored to a 39 or 41.5 if you want, but it may be cheaper in the long run to find one with proper jets/slide already in there. The 38 should add a little more bottom with less top if that is what you want (do you really need more bottom?

)
Hope this helps
DoldGuy