hi everybody!
new here, new to fixies, (and bike work in general) but i was wondering:

i have a late 70's (?) fuji that i want to convert to a fixie, and i have the hole rear wheel set-up, but
do i need to get a new crank or can i convert the ten-speed crank?
can i use a bmx crank and add clipless pedals??!?!

sorry if this is repost

edit: i probably will want to replace it anyway, as the pedal clearance is way too little, but still, i would like any input

You do not NEED to, but I would recommend it. Are they cotter-pin cranks? If so it might be a challenge to remove them. Check sheldonbrown.com for how this is done. If you do get new cranks, you will also need to swap the BB and make sure it is appropriate in terms of compatibility with your cranks/a good chainline (and the threading of your BB shell, which should be English). You do not need track-specific cranks, but just make sure whatever you use can be set up properly. Again, consult Sheldon (RIP), he is your god now.

all hail Sheldon

hi again, sorry, but i am unclear.

i CAN use a bmx crank and add my pedals?

If your old crank uses a square taper bottombracket and the bmx crank you want to use is also square taper than you'll be ok,but the chainline might off.