- Flywheel... there are a lot of those lying around with USLMRA Members pretty much unanimously going to the Billet Wheel. E-Bay you see them occasionally $10 - $15.
- Cam - $10 if it's in good shape. They do go higher, but I just bought 7 of them, averaged $8 apiece, plus shipping. Considering they all came from only 2 sellers, that wasn't much extra. Maybe $12 apiece into them.
- Valve Train - Valves and Lifters - Maybe $10 used. Depends on condition and how bad someone wants them.
- Rod - New you can buy it on E-Bay $21... figure half price used.
- Piston - Again you can buy it new on E-bay $28... half price used.
Intake valves don't sell as high as exhaust valves, most folks doing the head work on a Briggs for racing increase size of the intake. Springs aren't going to do a racer much good or George wouldn't sell so many springs. Retainers are a dime a dozen.
Price on the complete motor... depends on condition. Anywhere from $70 to $170 on E-Bay. Shipping will run you anywhere from $35 - $75 on a complete engine, depending on the seller and how they're getting the package to UPS.
Out of Canada that might run a little higher. Look into shipping options, there are legitimate ways around the delay in customs if they go out of the country, and it doesn't cost that much more according to the G-Man.