Sweet looking project. I like the pictures of all the new parts laid out. Another Suby conversion. Looks great!
You asked about the fuel sender. For my set up, I bought a universal sender and the correct guage from Summit. I'm also using Autometer guages, I spotted the yellow boxes. I tried to figure out the resistance of a stock sender. I figured either go with their gauge/sender and know for sure it'll work, or guess. I'd rather not guess with something like that.
Belt? The rope is a good idea. I worked for a little while at a truck part store. They had a guage to measure old belts if the numbers are worn. That might help in some way. They had a HUGE rack of belts. I know, I stocked it.
I have a thread for my project, it may or may not help with your subaru conversion.
http://www.germanlook.com/Forums/showthread.php?t=7050
There is also a Subaru advice thread, it may or may not help. Just thought I'd throw it in here too.
http://www.germanlook.com/Forums/showthread.php?t=6676
My only advice would be to raise the engine and transmission for better ground clearance. Also, it looks like the exhaust is as low as the oil pan. So why shorten it? I shortened mine and I almost wish I hadn't. I didn't gain much ground clearance.
Just my 2 cent.