Recently acquired a cm400 and I'm trying to find a cheap way to up my wheel sizes. I already found a local shop that can lace up the sizes I want, but I'm trying to get away for the $500 ticket

I came across a build thread with a guy who was running a 23" front wheel that apeared to have been swapped off of an enduro or dirt bike with a small drum brake, and an 18" rear wheel that looked kind of old, not like a rim swap and lace.

Anybody know what these wheels could have come off of? Thinking the front may have come off a cr-series or an xl-series enduro, and I'm not sure about the rear? cb750 maybe? Anyway, I'm trying to build a rat/bobber on the cheap so any info would be helpful!

Here's the pics, I love the way it sits.