steering wheels...
My wife got me a Nardi, years ago, for the tii. Dunno the size offhand. When I sold that car, the wheel went on the coupe.
Thing to beware of is that these wheels with the thin "spokes" have edges that can be rough on your hands. I've sorta gotten used to it, but if it weren't for power steering those thin spokes would be murder.
Nardi seems to be the default replacement but there are others. As noted above, the hub adaptor is everything. Don't get a wheel that doesn't come with one unless you're sure that you can get the hub.
Turn signals are activated in stock form by a "finger" on the edge of a flat washer that fits between the hub and column. The position of the turn signal (distance from the steering column axis) is adjustable within 1/4 inch or so, and there is a spec for clearance between the finger on the switch, and the finger on the flat washer. Clearance is quite small, on the order of a millimeter or few, but I don't recall it exactly.
Replacement hubs may come with the turn cancel finger "built in". Expect to adjust the turn signal to just clear the hub when not using the signal. Adjustment is held by two fat phillips head screws securing the signal to steering column.
Ordinarily when removing/replacing the wheel, I'll get the rotational position off a spline or few. I've learned not to tighten the big nut on the column until after a test drive, to make sure the wheel is centered. Last item... that big nut is likely on pretty tight, but doesn't need to be put back by a gorilla. It is a self-locking type and is unlikely to come loose; it would have to back out quite a ways before the wheel gets loose from the splines to become "a problem".