According to TRA's Judging Standards manual TS27000 to TS42000 may have one piece or split steering column.
FWIW, TS39781LO had the split column. The added mounting tabs on the frame, and the captive nuts on the firewall all looked original, so I'm fairly confident it was built that way.
The fixed wheel version of the column has a very short section of splines (perhaps 3/4") with a tapered seat just below them. The adjustable wheel version has much longer splines (3 or 4" worth) and no tapered seat.
As far as I know, the steering box for split column adjustable wheel is the same as the box for the split column fixed wheel.
But (in case it's not obvious), the box is different for RHD vs LHD. The threads on the worm are different, too. One of my bits of Triumph memorabilia is a brand new RHD worm