i know that 1505 cranks can be stroked but what size journals are needed to start with? i just got one that has 1.730 big end journals and was wondering if this is already too small a size to stroke?

Yes it can, you just can't stroke it quite as much as a std (1.750") one.
Still worth doing...
I'd just ask them to stroke it to whatever they can get with 1.625" finished size. Probably 2.6mm extra.
You could go further (use undersize bearings)- it just depends how many regrinds you want it to have left.
Matt Read (TheMiniMan) in Qld ground one to use -.080" bearings, but these are dodo dung now.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.