I've been tripping on 8.25 vs 8.5 trucks lately. And I've been wanting to try both:
I stuck three washers on the inside on the 144s. No 149 hot rod-ing. I was happy. A slightly more stable turn. I was happy. A tad more grind room. I was happy. Board not feeling quite as tight-rope. I was happy. Most likely nothing more than Placebo Effect than substantive difference, but either way, I was happy. 149 vs. 144...Game over.
Ha yeah, the washer game can really be a winner sometimes.
On a total madness run, because DLX 8.25 are wider than 8.25, so I almost needed a 146 mm hanger (which I do have as well in old Indy stock) but just with current products, I used Indy 144, Thunder 148 and Venture 5.6 hangers, added a couple more washers and then put on some machined down axle nuts, which were a lot thinner, so I could get the wheels to sit out that little bit more again. Machining nuts - axle or kingpin - is something I have been testing for a bit, but if I go too hard or long, it burns out the nyloc so is not so good, but it does work, taking them down a couple of mm, everything still fits on fine, I can get a lower profile kingpin, or make trucks / wheels sit better to the edge of a deck without having nuts sticking out.
Feels just right for not having a truck too wide for the deck and still getting slightly wider wheels to work well enough that I have decent hanger room and not showing the nuts or the inside washers.
Anyway, back to a normal setup, not something it takes hours to get just right, with quite narrow wheels and only one very thin washer on the inside of well worn 149s, things did match up fairly well too, as the axle ends were almost worn down too much, but I think in general the 8.25 trucks on 8.25 boards will match way better, added three washers on the inside only, just the nut on the outside and medium width wheels, everything should fit fairly well.
As to inverted kingpins, anything with nyloc can come loose, so Indy, Thunder, Slappy will at some point all come loose if the kingpin is put in and taken out too many times. If you are the sort of person to change out bushings or adjust things every other day or week, then any of those options might not be so good. Loctite has been said to help with this - still haven't needed to use the bottle I got for my inverted kingpins, because once things are set up, I don't really change bushings or adjust anything for the life of the truck.
Ace has a different technology, so that should prevent things from loosening on their own, but they do also have other issues, but maybe for some people, anything can and will break, more so than for everyone else. As has been said, you can also buy just hangers so if you are not sure, get a set of trucks and then get some hangers to swap in or out as needed too.
I have regular Thunder inverted trucks on the go right now too, just to mess around with them and they sure do give enough clearance and work fine in both 148 and 149 sizes.
Some people have said the Indy 144 just feel too tall on cast baseplates, so although you could get a set of Indy inverted kingpin baseplates and swap them in on the 149 hangers you have, you might not really need to.
Last thing to add, the Krux inverted kingpin set - just inverted kingpins, nuts, washers and tool - could also be a good option to use on the Thunder trucks if the baseplate has the hex head shape in it. Pretty much all cast Thunder baseplates since maybe 2020 have had that, no forged baseplates though, so I have been testing that out too - just hammer out the regular kingpin, easy and quick to put in the Krux inverted kingpin and can change the nut out if or when needed.
Some other brands of truck will need a lot more work to use an aftermarket inverted kingpin kit, eg Indy have a round hole in the baseplate, so you need to JB weld or something to get it to stay in there, so buying an Indy inverted baseplate kit might be easier. It is the same inverted kingpin as the Krux kit, so if that didn't work, you could just use those kingpins on a Thunder setup anyway.
Lots of options really, but maybe more than anything just figure out which size hanger works best and go with that. Anything you already have will be a lot easier to test and play with, more so than buying a whole lot more stuff.
* If you get Thunder inverted, get the 148s. They work great on 8.25 boards and balance things out nicely. Your comments about them made that easier, just need kingpin clearance on worn down ones, which the inverted option does give, so they will last longer too.