I did my due diligence and searched before posting so please don't berate me just yet....

I'm building a CX bike from a MTB frame for my first foray in to the sport; 135mm spacing.
It's aluminum, so fatter seat tube.
I want to run a single chainring and would like to put it on the inside so I can use a bashring.
The chainring I as planning to use is 46T, since that's what I had laying around.

So the question is, with what I got so far what sort of crankarms would I need to make it all fit, or is it even possible?

I got a set of double road cranks and a set of BMX cranks that will take two chainrings but after reading the info in past posts about running a single chainring setups I'm not sure if either of those would work.

A standard double road crank will work. You might be forced to use a triple (or MTB) axle length on the BB due to the wide chainstays.
Both Shimano octalink and ISIS comes in three different length. A standard road double is defiantly too short

Thanks for the reply Lectron.
My cranks are square taper, but I'm sure there are plenty of lenghts out there for those too.