Any conversion is probably going to work around a brushless outrunner motor. 2M gliders are usually between 1.5-2 pounds so you'd look for a motor that'd put out 150-200 watts.

Some of those are advertised as "400" size based on the old brushed motors we used to use. Look at motors that just advertise their measurement among the ones that're 25 - 28 mm diameter. Find one that matches your budget and look at it's specs. It'll tell you what strength ESC you need from the constant amp and max amp rating. The specs will also mention the voltage range for the motor.

Here is an example of a "400" outrunner's specs of a suitable motor.
It'll provide the power the glider would probably require, about 155W.
It'll be just over 1" wide. (but would need about 1.5" room)
You'll need a 20A ESC at least, maybe a 25A to be sure.
You'll want either a 2 or 3 cell LiPo to fly it. Look for one that will fit your fuselage.
I'd start with a 1500-2000mAh 3 cell.

I've made plywood firewalls for a couple of conversions. They don't have to be thicker than about 1/8" to be strong enough.