It's very easy to make these work with your '73 models. The biggest difference is the wiring connector, but even Ford used both a switch on the dash and a switch on the column for the hazards in early '74 models.
Physically, the columns bolt right up. Electrically it's easy enough to make them work either in conjunction with, or in lieu of, the dash mounted hazard switch. And the newer style turn signal switch with the single post instead of the dual post horn contacts simply needs to power a relay for the horn, because it can no longer power it directly through the column. Which in fact is a very desirable upgrade. I did that to my trucks even when I kept the stock columns. Horns work better and contacts last longer with a relay in the middle of the mix.
This means though, that you can't use your stock '73 and earlier steering wheel, but if you're going aftermarket that is not an issue. If you already have an aftermarket wheel, you'll need the appropriate adapter for the later style column.
The only other concern I can think of might be how your steering shaft is configured, or which steering box you have. But neither is a deal-breaker, and are very easy to deal with. Especially the steering box since you would be choosing your yoke/joint style at the time of purchase of the new shaft anyway.
If I've left anything out, I'm sure WH will correct that.
Paul