Wondering how this AutoMeter 3-3/8" tach mounting cup #5204 would mount to my 69 B-Body shift-on-the-column steering column without interference? Anyone try it? Would it need modified? Pics?

Not sure on the column-shift, used one on a 4-speed RR.
Try mocking it up first using a hose clamp through the slot in the mounting bracket.

I made a flat 3/16" strap and welded a spacer on the end that takes the place of the supplied mount. The strap is contoured to the shape of the column but does contact it. Back farther into the dash and our of sight lower on the column two hose clamps hold the strap to the bottom portion of the column.

Looking at the column that's currently out of the car, it would appear I have roughly 1-1/4" of mounting space between the dash pad and steering wheel shroud. I could probably call AutoMeter and see if they know the specific dimensions of the mounting block of their cup mount? Or perhaps someone here has the supplied mounting block they can measure? It's not horribly expensive but I'd rather not throw money at something that may not work right.

I debated mounting my Autometer Monster Tach on the column but I just did not like the redneck look of the straps. The 68-70 B bodies have a lovely overhang the dash pad attaches to. i inverted the tach bracket and drilled underneath the overhang. it's a piece of cake to reach the bolts if you pull the radio. I placed the tach right between the clock and heat controls and ran the wires up between the heat control panel and the dash frame. the tach is aimed toward the driver and is extremely easy to see with no obstructions. I'm running the shift light too. Gets tons of compliments.

Thanks for the advice. However, my Road Runner is a numbers matching survivor restoration which is why I'm not too keen on drilling holes in my pristine dash board. This is why I am open to a common less permanent day-two mod of installing an aftermarket tach clamped to the steering column as "redneck" as it is. Also I know a few people are using large black zip-ties to remidy the look of the more commonly used and accepted worm gear hose clamp. Just surprised no one here has the AutoMeter product they can measure for me?

Here's a few good tips if you are going to do this..
1. If you are going to mount it to the column using a hose clamp, cover the clamp with black shrink tube for electrical connections. It looks way better than a bare clamp.
2. If you want to mount the gauges on your dash in front of you, make a mount from two magnets and a piece of aluminum flat stock suspended between them. It mounts to most Mopar dashes right behind the dashpad and you can run the wires down the heating vent. You can Google "round magnetic base" to get examples of the magnets. To keep the magnet from marring the dash you can just spray the underside with black Plastic Dip.

I have had my tach mounted this way for over 20 years. Steady as a rock and completely reversible with no permanent damage.

I can also email pictures to you if you want...