http://1969stang.com/forum/index.php?/topic/54981-315-in-the-rear/

good forum and thread
search for —— backspace —- lots of info.

see www.69stang.com and vmf. its a debate. seems 285 and 295 for sure without mods. and some are at 315's. not sure of mods. you have a lot more room than my 67. i'm at 275. the biggest gotcha for me was understanding backspace does or doesn't (i forget) include the bead. and some where you may find the 'chart' of members and what they have. happy hunting!

on 69stang search for backspace. found 15x10 5.5 backspace 295 50s post with pics and clearance measurements. stock rear everything. post indicates room for bigger tighter.  i do think 17’s allow wider on front for your year.  on 67, 17’s allow for wider fronts. but in retrospect 17’s are somewhat out of place. but thats what i have. for vintiques at least bead is not included in backspace measure. my fronts are a little tight to the stock calipers.

so at thumbs up for charles. but please elaborate on.... well... the bias you’ve encountered.

398hp. 425tq

thanks for the pic. yes thats how far down the web pic shows the plate was notched for fit.
 

may i see pics of the factory shock tower plates for 69 CJs? and thickness of REF flanges? is it like - if you weld on thin flanges then REFs will not fit for other reasons? also can engine being higher or lower via engine mounts solve?  fpa’s have lots of room on my 67 s-code with factory plates. send fpa a trace of your ports else you may get back not so good of a match. fpa will work with you. tell them everything.

why cant the half inch stud be necked down to 3/8s at just the top and provision/seat for 1/2 nut in bottom of shaft mount?

Instructions are on the web and have several scenarios  but I am wrong about topping off first. Maybe metal can way back when said top off.