I've got a 1960's house with built with car deck flooring. I'm wondering if hardwood flooring should run parallel or perpendicular with these boards?

I'd like to run the hardwood parallel for aesthetic reasons. Haven't decided yet on flooring material but am leaning towards solid maple or bamboo, sand to finish.

Thank you for your time,
John

Are these deck panels flat and tightly together?

Yes, they're flat and tightly held together with the tongue and groove.

OK, OK... What the heck is "car deck flooring", exactly??

If it is solid lumber, you will have to go the opposite direction or a right angle to it, or over lay with plywood.

Hey Austin, I am thinking the poster means "Truck Bed" which are generally laminated panels usually of maple, about 12 inches wide, very long, and made up of narrow slats (about one inch) glued together. Usually 1 1/4 to 1 1/2 inches thick.
I almost think you could lay the top floor in the same direction if they are tight together and flat. I know this goes against normal practice, but so is using these panels as sub-floor in the first place.
Waiting to hear back from the poster before I commit to an installation procedure. You are probably right about adding plywood underlay, but im thinking this is a pretty rugged stable platform, and it may not be necessary.

I'm almost certain it's called car decking and a google search confirmed it. Maybe it has other names too. It's roughly 2x6 tongue and groove fir. The house is post and beam construction from the 60's. (Not stick frame with joists and plywood floor)

I'm thinking I'll need to put down a plywood subfloor.

Yes, given that it is Fir, if you wish to lay parallel to it, plywood underlay would be almost essential to ensure a stable installation.