Or is it a case of tighten to as tight as you feel right
Its unlikely that BSA would have even owned a torque wrench back then (?),
so if no torque figures are quoted in the official bsa literature, your comment is about official policy.
There are charts of suitable torque figures for common bolt sizes, and these can provide a useful guide.
20 to 25 ftlbs for 3/8" bolts, perhaps a shade more if they are hi-tensile grades.
And (considerably) less for smaller bolts.
And, stripped threads and broken studs don't a reliable engine make, so tighter is not always better.
But if it can come loose and damage something, it has to be tight enough.
Loctite can be useful insurance here.