Model580

I have a 1998 beachcomber model 580. I recently discovered that the wet end was leaking from the seal and likely had been for a while. Shortly after that I as well noticed a periodic sound that I suspected was bearing related. Bearing closest to the wet end seized up the other day. The pump and wet end are original and the shaft on the pump is pitted so I'm suspecting a new wet end may not seal properly due to that. I'm looking at getting a new pump and wet end because if that. Original pump is a 56frame 2 speed, 4.5 HP motor. Would a 4.0 or 5.0 HP motor work properly in this setup? Only asking as there seem to be some 4 and 5 HP locally on the lightly used market and looking to get it running again as cheaply as possibly. I realise that the inlets and outlets need to align. Any thoughts on this would be greatly appreciated. Thanks