Looking at the crank, it's missing the nub for a OWB (one way bearing) or starter shaft to start it. It does have a recess, so perhaps it's hollow and you can use a pin/spring like some engines have instead. However, most bump start higher end race engines are intended to be just that only as having a OWB/starter shaft decreases performance a bit by adding drag, so you may be hard pressed to find a crank/backplate/starter shaft/owb that will work. Not saying it's impossible, just a bit impractical. It could be impossible as OS may not make a compatible crank/starter for that engine, I didn't dig a lot.
A guy I bashed with many years ago bought a bump start lrp 30x and ended up buying a new crank, backplate, startershaft, owb, starter housing just to make it a pull-start. Was half the cost of the engine. If he was smart, he would have just taken it back and got the "sport" version of the engine that had a pull start on it already, but he was intent on running that specific engine in his LST2 for bashing for some reason. Odds are, any effects of porting or whatever that the "X" had was negated by the extra drag of the owb and perhaps partially deleted due to running a different crank (some of the porting is in the crank itself on engines).