As far as RIMS type mounts, you would have to modify them to make them fit. Probably the Aluminum RIMS, which are no longer made, would be the best candidate because you can take the mounting plate and the hoop clamps off, leaving just the aluminum ring. This would have to be "rolled" to the smaller diameter to fit a pre international shell.  Any good sheet metal shop will have a Slip Roller and can easily do this. The problem is you will have to figure out exactly what radius it needs to be rolled to.

Inde drum lab also makes a similar version that would lend itself to doing this. You could probably talk to Josh who is the owner and he might be open to modifying one for you.

https://www.indedrum.com/suspension-tom-accessory-brackets/brb

The other option is to use the Inde BR2 type brackets utilizing a home made adapter plate. The Inde mount has adjustable hole spacing so you should be able to make a round aluminum plate with holes to fit the drum and then holes for flat head screws to allow you to bolt on the mount. 

https://www.indedrum.com/suspension-tom-accessory-brackets/br2

As far as a mount for the bass drum, That is a hard one because of the unusual mounting hole spacing that Premier used. The toms used one screw in the center of the one piece long lug. The bass drums used one screw at each end of the long lug, not giving many options as far as some sort of retrofit mount.

Inde makes a bass drum mount that would work if there were two screws at each end. The plate is adjustable and has its own lugs on it so you just replace to two lugs with the mount and you are good, except you only have one screw per lug. If you were willing to drill one extra hole for each lug  this would work. You would however have to replace the front lugs with some matching Premier single ended lugs like they used on the floor toms and bongos. This would, however involve drilling one extra hole per lug. However, all of these four extra holes would be located under the original long lugs, so if you ever wanted to revert back to the original setup, they wouldn't be visible.

https://www.indedrum.com/ultralight-tom-holders/low-profile-drill-free-rail

The guy who owns and runs inde, Josh Allen, is a really good guy with a lot of innovative ideas. He used to work for Ludwig and designed the new line of Atlas hardware. When he left he started Inde and makes some really cool stuff.

Thanks for your input, I might give him a shout and see if he can help. Sounds like the kind of person who could. 

This is more or less what I'm looking for if I can make it work. 

My first instinct was to use a Pearl Optimount and modify it myself. I'm pretty confident I could get the radius right, and those are very adjustable. Unfortunately there aren't any drum stores which sell them less than an hour away, so I wanted to see about getting some feedback first. 

As for the bass drum mount, I think I will forgo one altogether and just rack mount them. I know it won't look 'right' but I dont think it would look wrong either. That lets me keep the old mounting bracket in the bass drum, which I may use for something else if I can find the right setup. The cymbal stands of the same era used the same sized tubes for example. 

Thanks again!