1980 Prop shaft u/j strap bolts

[stox258]

I'm trying to remove the props shaft on my 1980 and the question is, can it be removed without removing any other components and the screws that hold the staps on appear to be trx style heads. What size are they and what tool do I read to remove them? I have a set of sockets one of which is a Metric E10 6 spline tool, but I'm guessing the one fitted is Imperial and I don't want to strip the head, it also looks to be 12 spline. Any ideas?

 

[Oneball]

The bolts are a 12 point imperial head. Normal 12 point imperial spanner will be fine I think the heads are 7/16” but don’t quote me on that.

 

[stox258]

They are 1/4", can't believe they are so small for all that torque, but an absolute pain to get off....... Thanks for your assistance.