i have a 46t chainring and liken guide with this cook bros. crank. it has 110mm spacing and 175mm crank arms. i know these are mtb cranks but i have seen them on cross bikes. i wanted to know what my options are: could i use this crank on a single-speed? any mods necessary to throw it on a multi-speed cross bike? i really know nothing about messing with this type of thing so don't be afraid to be really basic in your explanations, thanks a lot!

on a multispeed bike.
I had a Cook Bros crank on an old MTB. Good lucking stuff till I cracked it.
I used a Shimmano bottom bracket.
If Both bikes are english threaded stick it on and see how
much it clears the chainstays. Might be alot.
I do not know what length you will need for a singlespeed.
What kind of frame is it?

i haven't made the decision for which bike to throw it own, i wanted some responses first on what bikes it'd work best with. i am thinking it will be awesome on a cross bike I am building up- but i don't have the frame yet. what kind of frame/bb would i need to make it work with the cranks?

The type of frame isn't the issue--I've had CBR cranks on MTBs, road bikes and 'crossers. The only problem I encountered with the road and 'cross bikes was trying to get BBs with really narrow spindles. I think the last bike I put them on wound up getting a 103mm spindle so the chainline would be right with a double chainring set-up. (That's with 48/34 rings, so if you're thinking of something larger, you'd want to get a longer spindle so the big ring and chainstay aren't in conflict.)