I’ve also tried 29er wheels in a 1990s frame.
Old narrow rim 29er wheels with 47mm tyres
I never took this any further because I had the Voodoo and other 26″ frames hanging around, but I did trial fit seat and bars, and can see no reason it wouldn’t be a good bike.
It’s a great way to re-use an old mtb frame which otherwise would end up on the tip, not to mention a nice cheap entry into gravel bikes. Those old Raleighs were quite well made steel frames.
About the only negatives are slightly long top tubes for drop bars*, and a small increase in BB height (not necessarily a negative especially if you want to ride fixed).
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*Try On-One ‘Brian’ bars and/or a shorter stem.