Questns about switchng MC, avoid 5port Jun block

there is a black rubber boot that came with the mc, the hole in the boot is super small compared to the push rod size that I'll be using, the same one that was used with the single mc already on the rambler. If the rod is just a little too big to go into the mc, I could get the rod lathed down by maybe 1/32 or 2/32, just to make sure it won't bind as it moves. 

I think I can open up the bolt holes on the mc a little and make it work, and use the two bottom holes in the firewall, but the dual mc is alot heavier then the single and hope the two bolts will be enough to hold it as time goes on.

The front port is 1/2

The back port is 9/16

Tomorrow I'll look at some adapters or reducers to connect the 3/8 nuts into those ports, and also a npt three way for the stop light switch. 

Wait a minute... You said use two studs with nuts.... I can't do that, (of course I can, just read on....) because there is threaded nuts welded on the other side of the firewall to accept the smaller size of stud used with the original, smaller mc, I'm sure the holes on this new mc are meant for studs little bigger (might have to do a fact check on that) and I would need to drill out the square nut to use the larger stud and nut... Did you mean "enlarge the mounting holes" of the mc, or the firewall? 

Also I was going to use the old rubber boot that's still on the push rod.