Re: 98cc Villiers on a 1945 Sears Roebuck
So glad you're doing this build. I'm both a fan of the old Elgin bikes and the Villiars 98cc 2 stroke. I have a build nearly roadworthy using that engine in a 1934 Elgin 4 star step through frame using a Tomos moped suspension fork and a three speed rear hub with shift kit parts from SBP. So, you can guess that I'll be following your build with great interest. Setting up the frame as you envision it will give you a lot more room for mounting your engine with the more swooping down tube. I'm also using that engine on a hybrid trike. No doubt you'll be done with your build before I finish either one of mine.
A couple of years ago an Australian formum member built a beach cruiser using that Villiars Midget engine which turned out very cool. Harry76 I think his forum name was. Curt will remember it. Intrepid Wheelwoman is also enamored ot that engine and can probably give you some good advice regarding its care and feeding. Good luck with your build and give us lots of pictures.
Someday when I grow up I will probably lose interest in toys with wheels, but until then...