Put 2 different sizes tires on same truck ?

I believe I would bite the bullet and put on pairs not singles.

It's 235 or 245 not 135.
I presume your spare is a 235/85?
If so then you have a matching set, get whatever you want for the spare.
You don't give much info on your truck but if the tires are the same dia within 1/2" you won't have any problems in any position on the truck.
4 wd operation needs same dia tires. Rear diff with locker or good posi needs same dia tires.
Steering axle, run what you want within reason. Different dia will make it pull like it needs an alignment.
Try craigslist, tire shops w used tires etc to get a matching size tire so you can get them all wore out and replace with new all at once IMO.

Replacing tires one at a time you'll never have a matched set. Re think your tire plan.

IMHO it is never a good idea to run different sized tires on the same axle… front or rear…

What you can do, get away with, or should do is the choice you have to make…

If its a 4x4 very bad idea (all 4 need to be the same size)need to do all 4 if two are very worn. ...... If it is a two wheel drive still not a good idea to replace one but you can replace just 2.

thanks all