RE: O.S. .15cvr pull start conversion
You will need a new crankshaft, drive adaptor, rear cover, and pull starter. This will be close to the price you'd pay for a new pull-start engine.
OSMG4475 21252040 CRANKSHAFT CV-RX $39.99
OSMG8219 21421300 REAR ADAPTER 15CV-X $11.99
OSMG8970 21812200 START SHAFT .18CVRX $12.99
OSMG8978 73003000 #5 RECOIL STRTR ASSY $42.99
These parts can be ordered through any hobby retailer who sells O.S. Max engines and accessories.