Oz,
In the 1980's Winchester built double rifles on their 20g 101 frame in a variety of cals up to 9.3x74R.
They have proven to be strong and reliable, but were jig regulated, and most require re-regulating to bring the two barrel groups together.
Re-regulating these "Grand European" rifles is not quite as straight forward as some doubles, but they can be done.
NT gunshith Vic Pedersen has done several and I've done a couple myself.
They can sometimes be bought for three to four thousand bucks or thereabouts, if you can find one, and come factory fitted with very high quality EAW QD pivot scope mounts.
I've shot one in 7x65R for quite some time and have taken a variety of game with it.
Winchester also produced combination guns on their 12g 101 frame.
Shotgun to rifle conversions on the Winchester 101 action have been done for quite a long time by gunsmiths and others, and the 1976 Gun Digest cover shows a 9.3x74R built on a 12g 101 from somewhere in Belgium.
If you can locate a 101 on the cheap, it could certainly be converted to a rifle, but I'm not sure how the cost of building one would compare to the price of buying a Winchester factory 101 double rifle.

My experience with 101 triggers has been happier than what Tinker has found.
I shot a Pigeon Grade 101 Trap and a Super Grade 101 trap gun quite a bit in the 70's and 80's, and never had any trigger problems with either.
My Grand European 7x65R has fired a lot of rounds (for a double rifle) and it has never suffered any trigger problems.
Hope this helps with your plan and please keep us informed as to any developments.