Well... for one thing, ya don't even need a lens with LF
You can have plenty of fun even with just a pinhole in foil, and making contact prints...
Actually, your 135s might well cover 5x7, at least at close focus / macro. One of the funnest aspects of LF is the very wide range of affordable lenses you can use.
One thing to watch out for: 5x7 film holders can be very pricey. They are in short supply. Do keep any eye out for them and if you buy oldies, test them thoroughly for leaks. It'll take some patience and some $$$ to build up a collection of good holders.
Here's another holder tip: chamonix does make 5x
8" holders. If you can adapt your camera to that, it may be worth it, esp. if you prefer the aspect ratio. Consider also that 5x8 is had from 8x10 by one cut. If you do the math you may see some wisdom in doing that. Also, believe it or not, 5" rol film is still available... that's what I often use for b&w in my 5x8 holders, 5" panatomic x roll film.
Enjoy!
P.S. I hand shutter all the time, no big deal. Why people spend megabucks on adapters for packards just to get up to that speed is beyond me. Experiment and have fun.