The spring lever on my right front wheel broke and I got a replacement
part, but I can't get the bolt out of the Height Adjustment Plate. The
threads are too big for the hole. Somehow the bolt was inserted through
the plate during manufacturing, but I can't figure out how. I have
tried "unsrewing" the plate from the bolt, but that is stripping the
thread and I don't want to do that b/c I won't be able to bolt the
wheel to the mower body.

Any tips on how I could separate these two parts so I can put the new
spring in between the bolt head and the plate?

Here is a diagram of the mower. I am talking about parts 76 and 79.
http://www.outdoordistributors.com/p...PARTS-LIST.pdf