SB-1018 is described as below,

Short block for selected Echo 2-cycle engines
includes abbreviated gasket set for short block installation
used on selected variations: CS-3000

The CS-3000 is 30cc. Echo chain saws use numbers like CS-xx00. The XX will be the displacement. Up to 50CC they have a beam mount. The SB-1080 is a super engine. It is beam mounted and 50cc. Past that you have to cut it out of the case. I have liberated two CS-510s and a CS-650. The cases are magnesium and come out real light. The trap is making a big aluminum mounting plate that weighs a lot. Keep it simple strong and light. I am now a fan of loosing the rear seal and covering the hole with a turned cap. That eliminates un-needed crankshaft and a seal that might leak. I think Ralph Cunningham did it that way.

I bought a CS-330T a while back in the clearance bin for $25. It had no bar. I really did not need another conversion right now so, I installed a bar and chain. It ia a really nice saw for cutting firewood. Who would have thought??