Andy,
A cheaper racing engine line sounds like a great idea! It would likely boost the sales of your pipes, hardware, parts and upgrades too. These are "complementary goods" - for example, if you can sell more potatochips you can sell more beer, and if you can sell more beer you can sell more potatochips.
I am confused on one point - your MAC .67 engine is listed on your website at $409.95. Is this still the price you plan to sell them for? If so, $350 is not that much cheaper for the cheaper design you proposed.
I agree with what you are thinking about selling resonably priced, user friendly "engine-pipe-fuel systems" that are easy operate.
Thanks.
Dave