Qualcast Cultimatic DeLuxe spares

I’m afraid that I don’t know much about the Cultimatic deluxe, but am fairly well up on B & S side valve engines. Your old one was a 4hp pulsa-jet with a flange on the timing case and roller bearing crankshaft. 4hp “horizontal crankshaft” engines are not that common but 2.5 to 5hp B & S side valve engines had similar mountings and crank height so a 5hp would fit. (there are still a few “new old stock” 3.5hp side valves about). Because they were used on many different things, the crankshaft was available with different ends so you have to get an engine with the same crank, probably ¾” dia with a 3/16” keyway. If something mounted on the flange round the crankshaft you will need an engine with a similar flange. Ebay is a good source of used engines.
Contacts in the “trade” did a lot of grumbling about how Bosch had ruined the Qualcast spares system a few years back so I recon you will have to find a dealership with old stock to get the parts you need. Bartram Mowers do Qualcast spares on-line, and tillerparts buy up old rotavator parts from dealers, then sell them on.
Regards, Richard