I guess it depends on what you consider "bolt on"? As far as bolting on in the exact location a standard VW Ghia caliper goes, no. Airkewled makes some kits that use the two/four piston Wilwood calipers with a caliper mount that bolts on in the location of a drum backing plate. So, technically they do bolt on without any mod/machining, just not in the exact location of an OEM VW caliper.
Edit: Holy crap! No replies in a day, then two a few minutes apart! Mike, what aftermarket performance calipers use the stock VW caliper location?
Some front "talbot horizon" 48mm pistons and "talbot simca" 44mm pistons are bolt on calipers on beetle spindle.
There is 3 different talbot horizon models with different pads which can bolt on (small, medium and large pad) they become hard to find because these car were product during 70's 80's. These calipers was recently available reconditionned by "budweg".
The main issue with these calipers is there weight, especially the 48mm, whereas the 44mm are very similar to bug caliper and have the small pads (rabbit mk1 pad) which are the better one because "less blocking wheels" and not "singing" when you curb slowly, small pads also on 1 of horizon calipers.
I bought a pair, new/budweg, of 44mm one year ago on amazon, Lucky...
If some are interesting i can find all exact references...
Here a pic of a 48mm (medium pads) pair i sell (because found à 44mm pair last year)
Here a 44mm new caliper from budweg (ate reconditionned)
If i have few time i will try a pic with the beetle caliper near the 48mm and 44mm despite the 48mm are already package...