ams511
Contributor
Based on your info, it appears my later generation MK 5 does have the 'heavy' yoke since the '3000 psi' stamp is on the end of the yoke next to the metal banana-shaped yoke screw. My older generation MK 5 will likely remain in reserve as a parts-donor/reserve reg, as it only has 1 HP port, and I don't know how much luck I'll have locating a spare 3000 psi yoke either.
In my opinion you are over thinking this. Although the regulators are old there is nothing inherently unsafe about them. I have several MK-5s and don't remember ever seeing one with a 4-port turret having a skinny yoke. The skinny yokes I see are usually on the older 2 lp port variety. However, I could be wrong. As AWAP mentioned there are three yokes used on the MK-5, thin, medium, and thick and the latter two are fine for 3000 psi service. Some people even use the skinny yoke without issue on a 3000 psi tank.
If you have the spec version it can be filled with lube the same as your Atomic if you so desire.
My understanding is that the MK-5 is still officially supported. Some parts are not available. If the regulator is covered under parts-for-life and something fails that cannot be replaced, Scubapro will "upgrade" the user with a new regulator. If the regulator is not under parts-for-life, your friendly dive shop will offer to sell you a new regulator. Remember, the youngest of these regulators are 20 to 25 years old, so the Scubapro parts stockpile has been depleted.