I am a firm believer that 5 hsp NOS Briggs motors make wonderful birthday presents. And a Simplex for Christmas is always a good choice in gifts. Rusty old Indians or a barn find Excelsior are other nice gift options for boys who never grew up.. Thank you, Santa! I've been good, honest!
What a wonderful adventure you have ahead of you, my friend. I'd go for the Briggs and make it your bike the way you want it and not necessarily an exact restoration. Besides, every time you are asked about it you can say, "my wife gave me that engine". What an awesome thing to have that kind of support from your spouse. The bike will always have something of her in it and be a reminder of what a lucky fellow you are.
Nothing says you can't make your Simplex an improved version of the factory model. Electric start... woohoo! And better brakes. I look at that seat and visions of some nice foam padding and black harness leather come into my mind. If it were mine, I'd also want it street legal, licensed as a motorcycle and ride that baby for the rest of my days. Vrooommm...
Must be in the ethers that we keep wanting to raise the bar from motored bicycle to light motorcycle. Look at some of the great builds going on now with the big HF motors. My next build, too, is morphing into the grey area of light motorcycle... my convertible tri car Indian/ Hiawatha with canoe sidecar and interchangeable tadpole front end... powered by a light motorcycle engine, a German model 1932 Fitcher Sachs 2 speed 2 stroke of 98 CCs. The frame started out as a Worksman NB and now has a frame more like your Panther. I don't know yet if I'll try to license it as a motorcycle. I'm so excited, as you must be with the Simplex build. Fasteddy is coming next week from Vancouver to spend the summer working on our Indians and sidecars. How lucky we all are to have these great projects and a community of brothers and sisters to share them with, cheering each other on.
And here I was thinking your Panther was special... now the Simplex will take center stage. I'll be following that thread, sir. When the time comes that you're doing your seat, let me know if there is any way I can be of help to you. It would be an honor.
SB