Hi,
I use the Pentax 67II with a Macro - TTL-Ringlight and I do mostly Macro photos. I have the Macro 135mm lens, extension tubes and I newly accomplished this by the original Pentax 6x7 bellows. 135mm without tubes is great for portraits, 135mm with the whole set of tubes gets you down to 1:1 and 135mm with bellows even beyond. Great advantage of the bellows over extension tubes: a double cable release allows automatic diaphragm. If you like to get even closer, you can turn arount the front board of the bellows, which allows you to use the standard 105mm lens (or any other lens with a 67mm filter size) in retro position. With a double cable release, even then with automatic diaphragm. Great advantage. The bellows for the 6x7 has a much longer extension then any other 35mm or MF bellows on the market (350mm!!). If you use the Pentax 645/645N/645Nii, iŽd recommend the 6x7 bellows over the 645 bellows for its much longer extension.
In short: For Pentax MF Macro work 135mm macro lens and tubes and bellows (of course you can add enlarger lenses with that one aswell).