Welcome, the x-flow is a cracking engine in a Westfield, particularly in a live axled/four speed narrow body car. Lots of weight saving compared to a more recent engined five speed indy wide.
If you've only just bought it/are new to Westfield type cars etc, then TBH, I'd do no more than give it a close looking over this winter; Do the fluid changes so you know where you're up to on engine oil, coolant, brake fluid. Check gearbox and diff oil levels. (You don't normally change those, just top them up as required).
But really, you're probably best just servicing it and making sure everything is sound, only replace bits that are knackered or damaged. The main thing, is to just drive it! Get used to it, preping it for sprint/hill climb use is pretty straightforward. But spend some time finding out what you like/dislike about the car.
Engine changes, (where you go to a different type of engine) aren't cheap, in fact really, unless you're doing it 'cause you enjoy the tinkering, and there's nothing wrong with that, they rarely make sense economically.
Five speed box isn't important for most sprint/hill climb courses and the four speed is lighter, which is important!
TBH though, purely from personal experience, and what I've observed others go through, unless you're up for the engineering challenge of developing a competition car, don't bother. It's frustrating, expensive and time consuming! Much better to just do the prep work to make what you have eligable. Run that for a season, find out which class you want to be in, type of circuit/track you like, and then look at buying a suitable ex-sprint car that's already had the work done. One or two come up on here most years as other competitiors change groups etc.