Hi Karl,
My original BN2 steering wheel rim measured .750" x .750" X 16.75" diameter outside to outside.
My replacement Moto-Lita wheel rim measures .750" x .850" x 15" diameter outside to outside. See pic--
The rim still feels strangely skinny to me, harder to get a firm grip on, but not a big problem. The smaller outer diameter actually gives better road feel & more room to maneuver. There is no noticeable increase in steering effort, but the BN2 is a couple of hundred pounds lighter in front than the later cars. I can easily turn the wheel lock to lock with one hand & the car stationary. The 15" wheel gives about 12% increase in steering effort. A 14" wheel would give about 20% increase in steering effort. If yours turns easily now the smaller diameter may be ok.
I used a Moto-Lita hub which fit perfectly with the original turn signal/horn button assembly.
Aside; the Big Healey steering wheels always had the spokes located at 120 degrees with one at 12 o'clock. This gives a fairly unobstructed view of the gages. Many replacement wheels have one spoke up & two spaced at about 100 degrees. I don't know if it matters to you, makes it harder to see the gages.
D