340 Main caps question
If you don’t have any of the caps, you want to call Kent Ritter and buy a set of his billet caps.
Buy once, cry once. They are 4 bolt caps but his rear main cap is fully machined. Much cheaper to install.
You can cut the outboard bolts off the three center caps and just use the inside bolts.
I would not mess with any other caps. You need all 5 so just suck it up and start with those.
You can probably find some X or R block take off caps. Those are plenty good enough for what you are doing. Those rear main caps are fully machined too. Ritter may even have some 2 bolt take off caps you can get from him.
That’s about the best options I know of.