Considering the lack of PS, trading it off may be the right idea. Also, I'd trust the advice of the Massey gurus before mine.
However for older tractors in general, I was going to mention that [within reason] the actuall capacity of the loader isn't as important as the operator's judgement [possibly important considering your option of using the loader on a later purchase too]. I've seen Farmalls [F20] and even smaller tractors with Farmhand10 loaders cobbled on.
If you need the capacity for just lifting, I wouldn't think you'll have trouble, but when you start going over rough ground with a load, the effect on the front end can be really multiplied. Dirt work can put stresses in directions you wouldn't imagine either [both digging and, when lifting, dirt tends to be heavier than you'd guess].
Good Luck! /forums/images/graemlins/smile.gif
<font color="red"> edit: should mention why I said within reason, though its probably obvious; the larger capacity loaders are built heavier themselves compounding the potential weight </font>