This has a 1-1/8" (28.550 mm) shaft. PTO Mtg Face 3-11/32" (85 mm). The replacement engine is CH23S-76510. If you use the CH740-0084 engine there may be minor differences but parts should be interchangeable as needed. The shaft is a little longer but it is drilled and tapped 2" deep and the shaft is not hardened steel so it can be cut down if needed. You will have to use your muffler from the old engine. You would also have to make sure the canister air breather would not interfere with anything.