What length steering column?

I'm to the point in my build that I'm looking for feedback from those that have installed tilt steering columns. I'm looking at Flaming River and Ididit floor shift columns. Am I correct in my understanding that 30" is the "standard" length for our cars? FWIW, my rack is a power unit. The input shaft is 3/4“ / 36 spline. I know there are countless adapters so not anticipating an issue there. 
I'm wondering about column length, mounting, and sealing at the firewall. Also wondering if anyone has installed, or seen, the "roadster" style in our cars. Any suggestions would be greatly appreciated.

Can't answer your column question but your roadster question sound like it could be a fun thread.
The way you state the question kinda implies it was a version or option from Classic Roadsters. If so, then no, never even heard of that.
Otherwise, yes, but there's a broad definition of a roadster. I believe it's always topless, one- or two-seater only and totally built for speed and cornering.
One of the better examples i've seen is in a recent post from SaxonFord. It includes a frameless windshield and some subtle body mods.

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Cool! I didn't know there was such a thing.
No, what I was referring to is a catchy marketing term FR uses...
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A 30 inch column seems too short. Take a look at Flaming River's custom order diagram and measure your car taking into account where you want the steering wheel to end up and the amount of column that protrudes into the engine compartment. I ordered my FR custom tilt column at 38 13/16" long.

Some additional info/considerations: FR's "roadster-style" column uses a 5 1/2" bell shaped transition to the tilt mechanisim, all of which would have to extend out from the dashboard. Since I'm 6' and the seats don't go very far back I needed the steering wheel to be as far forward as posssible. Therefore I used the standard tapered shape cone transition which allowed me to bury some of its length behind the dash face. My column only extends 4 1/2" out to the wheel. The typical column drop is attached to the factory underdash bracing and the floor mount is their swivel mount. Very straightforward installation.

AHSebring64 wrote:A 30 inch column seems too short. Take a look at Flaming River's custom order diagram and measure your car taking into account where you want the steering wheel to end up and the amount of column that protrudes into the engine compartment. I ordered my FR custom tilt column at 38 13/16" long.

Thanks for that! I came up with 30" because the build manual says the MII donor car's steering column can be used and I know it measures 30". I was thinking that was too short. Yet another build manual misdirection.  
Thanks too for the tip about FR's custom column diagram. I didn't know that was a thing. I'll be sure to look. I too am 6' so I'll be needing something of similar length. You give a good description of the differences between the roadster column and the standard. Sounds like the roadster column would look like a Q-tip sticking out of the dash.  

Just out of curiosity
What is your height? as I had the same question