Serendipity Doo,

I found just what I was looking for; I love the internet.

What the doctor ordered. The rear assembly of a Mega blaster that can be adapted to my construct with a minimum of alteration.

Just assemble a couple of boxlike structures and attach the elevation drum gear.

https://i.imgur.com/SoCrJHv.jpg


Then somewhat faithfully copy the detail and we'll have the suitable energy producing end of the Helstrum Megablaster.

https://i.imgur.com/a8xT5Jh.jpg


I even have some of the armour to replicate.

Ahhh! It;s Christmas.