16 tooth crankshaft

I am trying to distinguish which crank I have in this bottom end.I know it has 16 tooth centre and no woodruf key on the end,but its in z1 cases.I suppose my question would be what are the differences between a J crank and a Mach 11 crank?

If it's 16t and takes a roller chain it's a mk2 crank.
They drop straight in to all kickstart cases with the matching cam sprockets and is a popular upgrade.
The 'J' crank is easily identified as it takes a hyvo (silent type) camchain .

Are the rods the same length as well or do I need to use a spacer to correct.I will be looking for the proper top end for a dragbike build,thanks for the info

Yes! The MK2 rods are the same so no spacer needed for that reason.
It is the 'J' onwards rods that are shorter.

how about the stator cover will that have to be swapped out for a 79-80 model?thanks

Yes! the MK2 alt is different and needs the matching cover to mount the stator coil.