I put a 14" wood Mountney on my 78B a few years ago to replace the ugly “rubber” stock 15” steering wheel. But a short time later I ended up replacing it with one of those really sweet 1" thick 15" wood wheels that Moss sells. It's kind of funny but I can never say I didn't like the feel of the 14" wheel while driving, but the reason I replaced it was because I thought that it had horrible build quality and was kind of cheap looking.
Thinking back I didn’t think the 14” obstructed the Tach & Speedo gauges, but it did kind of block the view of the other gauges (oil, temp, fuel & clock).
But whatever way you go its really up to what you like.