I can't quite figure out which Workmates you have. If we stick only to floor-standing ones, I think you described three of yours as being "full sized": 1) the "x-frame", 2) the 200, and 3) the 425. If the x-frame is what I think it is, then the only one of those that I would call "full sized" is the 425. The vintage 79-001's would definitely be heavier than the two smaller floor-standing models you mention.
If you're going to look for a 79-001 to buy, you will find mostly Type 2's and Type 4's. Others show up less often than those two. You can read about them on these two pages:
https://h-frame.weebly.com/79-001-type-2.html
https://h-frame.weebly.com/79-001-type-4.html
The variation in weight between them is minimal, between about 30 and 32 pounds. How much does your 425 weigh?
I don't know of any comprehensive type study on any other Workmates (such as the 425) other than mine for the 79-001. This seems to be true even for European models, because I have received comments from European owners wishing for one.