That is a good bike to use considering that it is a cantilever frame design.
Do a forum specific search on "Del Mar" for more info.
That said, beware of the fenders!
There are plenty more posts on the subject if you feel like doing a search.
Also, I cannot stress how important it is to clean and repack the wheel bearings with good quality automotive grease before you put any kind of strain or speeds that bolting an engine into it can do. The factory grease is junk. It is also a good idea to clean and repack the pedal crank and fork neck/ steering bearings with the same quality grease while you are at it.
Any bike worth upgrading with an engine needs to be taken care of properly to endure the extra strains and stresses of engine power.