Wow, lots of traffic on this one. I forgot to turn on notifications.
I don't know what the stock scrub radius is, but here are the wheel fitment calculator numbers. They assume 0 scrub to start. The OEM tires/wheels are 235/75 R15 on 7" wide rim with 13mm offset. The Camaro wheels are 245/45 R20 on 8" rim with 35mm offset and a 25.4mm (1") spacer. So the calculator says the scrub radius is now 4mm from where it was which is about 1/8" so in my head that's a wash.
The way I understand it is really the hub shouldn't know the difference if the centerline of the wheel stays in the same place. I don't think the hub would care because basically the spacer is acting if it were welded to the back of the wheel (conceptually speaking).
On bearings, always put in a matched bearing and race whatever brand you use. If you want to run timken bearings put them on timken races, knock the chinesium races of questionable metallurgy out of the new rotor and put the one matched to your bearing in.
There can be dimensional differences in diameter and width of rollers from brand to brand so brand x races aren't always the correct specs for brand y bearings.
That's interesting you say that, because at the time I wasn't thinking about it and also didn't really have the means to get the races out of the new rotors, which were AC Delco for whatever that's worth. So yeah, I did put Timken bearings in on whatever races that were in there.
I bought React Suspension 2" modular drop spindles earlier this year and also found out my neighbor was a machinist for 20+ years and was looking for some work so I asked him if he could make a hybrid hub with the OBS bearing dimensions and a hub flange that ends up where the spacer was so it is just one solid hub. He was up for it so I had him make them out of some 4340 heat treated steel and I bought some CTS calipers and rotors which are the same as the Camaro, they just have the flying V on them. So now we just need to make a bracket for the caliper. Anyway, long story short, on the new hubs I pressed in the Timken races that came with the bearings.
My gut feeling out of the whole thing is that I probably overtightened the spindle nut and/or didn't have enough grease in the hub. I only packed the bearings and didn't add any more in the hub. A couple people I've talked too said it wouldn't hurt to put a little bit in the dust cap and on the spindle too, but not packing the whole hub full obviously.