I doubt the 1961 car matters, just the engine. Is yours the rarer aluminum block? If you don't have power steering, easiest is to adapt a mount to bolt on the pad for the power steering pump. Syed in Malaysia did that and posted many photos a few years ago. His brackets were custom, but I have a "York to Sanden" adapter that looks similar and an easy fit. Sold on ebay (~$60), get the one with the integral tensioning slot. You will have to source a fan belt, but download a Gates V-belt catalog to pick a PN. They come in 3 widths and ~2" increments of circumference.
You will need more pulleys on your crank. Easiest is a junkyard one from a later car. I recall that your 1st pulley is integral w/ the damper, which I think continued for all slants, so the other pulleys bolt to the damper. You might luck out and find an Aspen/Volare slant w/ the Sanden brackets (I did). Another bracket bolts to it for a Saginaw p.s. pump if you ever want that.
Yes, one company sells slant Sanden brackets for ~$250, but hard to make out. One member here used to make and sell them. I posted a few years back on all options w/ photos.
BTW, a Sanden is not rotary. Early ones are 5-piston (ex. SD508 ), and later ones 7-piston. Each is actually a double-sided piston so 10 or 14 pulses per rev. They come in ~4 lengths, w/ H15 being most common and what most brackets are for. Some rodders like the shorter H13 and I have seen an H14. Front holes are all the same. Whatever oil comes in it can be drained & swapped. I prefer the new PAO 68 oil.
Haven't seen bracket to adapt to the Mopar RV2 brackets. That would be like stacking a hippo on an elephant. You don't want the brackets to weigh more than the compressor.
