Just did that:

ECHO CS1080 shortblock, New from DLSMITH_23 on ebay $124
Farmers exchange wants about $210

Walbro WT-542, ECEDWARDS_TOOLS on ebay, $15

IF you don't have a lathe then go to,

Brillelli Customs for:
a prop hub $30
intake manifold $27

Get or make a muffler, ~$50?

Buy an ignition , ~$80

About $280

You now have a BME 50 clone!

$124 bucks for a little engine? I would not do that. Harbor Frieight Tools has Poulan chansaws for right at $100. They are very good for conversion. Use the engine and sell the rest on on EBAY? The weight will be simmilar, just throttle back. I got a thirty something CC echo saw at OSH for $30 a while back, no bar and refirbished, it was new.

Here is one on EBAY now:

http://cgi.ebay.com/Used-Poulan-Chai...item5ad669d0d6