updating a 69 fairlane 500

[Russ#26]

well about 8 months ago i picked up a 69 fairlane 500 fastback with plans to have a bit more fun with this one than the many other projects i have. problem being is that ive been stuck in the ways of old building just old style suspensions or making whats there just a bit better with some easy bolt ons.

ive already gotten the front end apart and replaced what needed to be to get it streetable for me to drive it and have fun, but i want more.

so far my only suspension modifications are

Wilwood 12.2 front disc brake kit
SS front brake lines
mustang SVO 1-1/8 master cylinder
maier racing 1-1/8 front swap bar
moog problem solver strut bushings, ball joints and tie rod ends.
upgraded the rear shoes from 2" wide to the 2.5" wide

need to do a ball and stud kit soon as well.

ive got on the shelf
12.2 wilwood 9" rear disc brake setup
wilwood brake line check valve and adj proportioning valve
SS brake lines
ranger aluminum 1-1/8 master cylinder (to get rid of power booster)
3/4 rear sway bar
9" axle with 31 spline axles and Detroit locker 3.70 gears

wheels currently on car
15by8 magnum 500s. 235/60r15 4.5" bs (but are spaced out 5/8 of an inch at the moment to clear brakes as inside of wheel is too small)
15by10 magnum 500s 265/50r15 5.5" bs

now what i wanted to start out with was a new set of wheels so i can put the magnums back onto my 70 Torino convertible. im looking into 17 and 18" wheels but im having a hard time with how the rate the offset of wheels today, instead of doing it in inch of backspace, etc.

the wheels i was looking at had an offset of +24 for the 17 by 9 and +27 for the 17 x 10.5, but if my calculations are right (with a bit of guestimation) i would need a 1" spacer to get these to clear.

most of the new age wheels i am not a fan of. i did take a liking to some of the newer mustang wheels like the ford gt rim and the fr500 rim, but not so sure on the use of 1" + spacers.

what would be the MM offset i would need to start looking for, for a new set of wheels? and any certain places that sell a good amount of wheels with the muscle car offsets??