You need to use the model and spec number off the engine. The replacement will a 'service' carburetor meaning that the throttle and choke shafts as well as the fuel inlet fitting from your old carb will likely need to be installed if they are still serviceable. A lot of different Tecumseh engines used the same basic carb.

I cannot find any numbers on the shroud?

Is it on a piece of equipment that has engine look up via the manufacturer? IE the Toro site? If you found a similar piece of equipment with a like engine and controls, you'd get there too I'd guess.

MTD snowblower-5HP Tecumseh snow king-14 years old.I have done a few of these carbs and I always use numbers from engine shroud.This one HAS NO NUMBERS on it.

Would you think it to be an HS 50 (small frame) or a H50 (Medium frame)? Any chassis #s? A bulb type primer or hold in type spring loaded metal plate thingermajob?

5HP with rubber primer.I would guess a HS50.Looks like my 8HP Tec. on an Ariens ST824.Only its a 5HP on an MTD.

The medium frame would be more like the 8 hp. Here's what I would do. I tend to go to toro.com parts look up. It's easy for me as many of the Toro model #s roll around in my head. Plus, you can use their search feature if you have the series to get the right model you want. They also tell you the year.
A real popular thrower was the 5hp 21" - model 38052. Select the year, look up the engine parts and let Google do the rest. The 5/21 has a small frame Hs 50 or likely Hssk-50. The small frame engines had a longer intake manifold.
Toro made a 5HP 24" model for years that MOSTLY had the medium frame engines. H50 or Hsk50 probably. The larger frame engines just had a little twisted adapter plate in between the carb and the block. 38040 comes to mind.
So, the easiest way to tell is the intake manifold.
If you want to compare to your 8Hp -38080 would get you there. You could post a pic if you'd like.