Ouch!!!
Sorry 1969, I've done a little checking,(only a little) and have'nt heard anything good about the guy. I've heard, I wont say from who, That he was banned on the OTHER site, Changed his name, And started the same stuff all over again. I know this is a hard one, but most of the people on this site really are a great bunch of people. Heck, If I had any good used engines left I'd just give you one. Someone here still might have a decent, new or used, engine they could let you have real cheap. Just do your homework first. Ask around and check out anyone you might do business with. Also, as long as you don't live in California, you can get engine kits a lot cheaper than $420.00. And here their still only around $200.00. add a little for the carb ya want and it still isnt $400.00. I was checking around to get another engine for myself and it looks like MOTORBIKEKITS.com is selling them, even to california, for $179.99 + shipping. Still kinda high I think, but prices have gone up lately. If ya don't live in Ca, and I REALLY hate to recommend this guy, But Boygofast probably still has the cheapest. I've never had a problem with him but some people have. Just go to e-bay and and type in "bicycle engine". You'll get a LOT of engines and parts there. I just did a quick check and Luckyearlybird,(we all think it's Boygofast's wife) is selling a 49cc for $169.99 with FREE shipping.And Boygofast has an 80cc, (Z80 Black) for $145.00 +$34.99 shipping. Thats still a little less than half the price you were trying to get the other one for. and you can always upgrade later. So, sorry bro, Looks like ya gotta start saving your spare change again and order one from someone you can trust. (Trust is a strong word,) perhaps "a little more confidence in" is a better way to put it.
Good Luck,
Big Red.
P.S. I just noticed you DO live in California. Good Luck.