Re: i purchased a 2006 Baja H2X No no motor or lower unit theft recovery.
From 1997 onward, HP didn't change so much in the GM engines adapted for marine use, so you'd really not be going down in power. If so, it'd be a slight drop off vs a more modern engine.
First, I see no particular goal that you have set. Well, you sort of have a goal, which is to put an engine that fits in the Baja as cheaply as possible, which sounds good, but will get expensive if you leave out details/musts going in.
Honestly, you need a better goal, like this for example: An engine that fits the Baja marine application and use (or can be adapted easily), which produces 320+ horsepower, for X amount of dollars (only you can tell us what the X goal is).
You are hunting and pecking. If you can get something specific in mind, you can start spec-ing out engines.
Can you mention your budget?