Dumb backspacing question

[rs50pilot]

So I have a 70 short fleet. I am building a new chassis for it but I cannot stand the wheels that are on it now. It is a coils spring, drum brake, WIDE rear axle truck 6 lug truck.

I bought a 69 LWB frame, shortened it and am giving it the full no limit suspension upgrade.

So the wide rear axle went into the new chassis and the short rear end went into the truck so I can still drive it.

I want to run 18x9.5 all the way around. Since it still a 6 lug I want to buy 5x5 wheels and use 6 to 5 lug adapters just to get these ugly wheels off of the truck until the chassis is done.

Only adapters I can find are 2 inches wide.

So wheels I want have 5.25 backspacing.

With the current drum brakes and a 2 inch spacer along with the narrow rearend in it now, plus a 2 inch spacer. Will the wheels work when I finally finish my chassis with the no limit wide ride front end and go back to the original wide rear end?

I'm just looking to be able to use the truck once a week. If I have to cut a turn short thats fine. It has a 3/5 drop on it now.
I have read so many posts and taken measurements. My head is spinning. Hoping somebody has clearer thoughts than I do.

[Overdriven]

The 70 1/2 and earlier width is 62-3/8" from wheel mount to wheel mount.
The 70 1/2 and later (up to about 78 or so) width is 63-3/4" from wheel mount to wheel mount. So do your measurements and figure the short rear with 2” spacers is 3-3/8” wider overall or a little less than 1-7/8” per side. No idea on the front with No Limit Wide Ride.

Personally I can’t see spending $ on spacers that you know won’t be used for long. Besides, the ugly wheels can serve as motivation to get the chassis done.