Rear wheel offset?

Hi all,
not so long ago I bought an 82 imported from the US and my aim is to change it into something street trackerish bit by bit. One step will be to replace the steel rims and horrible tyres it's currently shod with .... so I also bought some alloy rims + stainless spokes from Mikesxs. The rear is an 18" to replace the 16". I have to replace the shot swing arm bushes (already got the needle roller kit) so now seems a good time to get the wheels rebuilt while the swingarm gets powder coated.
I need to farm these jobs out, but maybe I can save a bit of labour cost but unlacing the wheels myself. So, the question is whether there's an offset on the rear or is the rim central to the hub flanges? Whoever builds 'em back up will need to know.
Any advice?

centered on both wheels

Blimey James, that was quick! Thanks - I figured the front was, couldn't really be any other way, but that's good to be sure about the back.
Thanks again

If you're up for it and have the time, you could re-lace the new 18" rim and spokes to the rear hub yourself. Lots of searchable info on the site that gave me confidence to give it a try when I did the same conversion a few years ago. I have an '82 Heritage Special with the double-laced spokes (48 rear, 64 front), so it was a bit tedious, but I enjoyed the challenge.

Excellent - I needed precisely this information!