The Dot 1s were more prone to leaking, but they were still a dependable engine. We never had one come in that was blown up, usually just worn out.

Dropping the Dot 4 in the 105 shouldn't be a big deal, but you'll need to change the front covers around to mount a 2-105 engine in an 1850. Either that, or do some drilling and put some motor mounts on the front.