Transformers questions by newbies, and not-so-newbies

[SilverDragon]

Is there a reason why G1 Lord Zarak is so disproportionate to the Scorponok body? He's the same size as all the other headmasters isn't he? Yet in robot mode the bulky scorpy looks a bit puny with that head..

Scorponok transforms into a city. Lord Zarak transforms into a roughly human-sized humanoid. Hence the size discrepancy.

More accurately, likely because, as you said, the Headmasters were standardised in size, likely so you could swap heads around freely.