Way back when I purchased my 29 Sport Coupe, it had a later 30/31 Gemmer column & box in it. I found a spark/throttle quadrant collar for the 28/29 column jackets. I cut approximately 1-inch off the top of the later type jacket I had and fit a new bushing into it to get the shorter jacket. I purchased the shorter steering shaft and rebuilt the box. Luckily it already had the new style worm bearing in it. I had to shorten the throttle & spark rods to fit and install a 29 keyed steering wheel & appropriate length light switch rod to top it off.
I recommend having all the parts in hand before shortening the column jacket. I cut it long and whittled it down until every thing fit right. Having plenty of accurate measuring tools is a must. Good quality photos of the 29 units also helped a lot.
It's easier to overhaul a 7-tooth box nowadays since all the parts are available. If I'd had one I sure would have used it.
The Gross unit is probably has the most advantages. It is a bolt in conversion and gives a "power steering feel" when driving and parking.
The do it yourself conversions with either an F1 or F100 steering are considerably cheaper IF you can do fabrication work. They also have the advantage of self cancelling turn signals.
Prior to buying my first 'A' several months ago my mechanical experience was mostly changing fluids and grease gun. Years ago changing points, condenser, timing.
My Dad was a machinist but I am not. I like "bolt in" options.