New Zealand Datsun Club

If you don't know what you are doing. You are better off to send in your short block to check bearing clearances and end float, especially since you are swapping cranks over.

yeah thats the plan find a new crank and get everything measured up for bearings and get crank balanced etc too

Get your wole rotating assembley balanced as one.
1st they balance your crank. Then they'll fit the front pulley, and balance that. Then the flywheel, and balance that. Then the pressure plate and balance that.
Mine was done at engine reconditioning services. They're in the east end of st aspah street. (Or at least they were?)
Probably wont be the cheapest, but their machine is very sensitive.

i take it they balance it all outside of the motor? doesn't need to be in the block? can they check it and machine it for oversized bearings if need be?

No.
They do it with the parts removed from the block.
if your engine hasn't been balanced before, you're going to have to have your rods and pistons balanced too. You'l have to remove them from the block to have that done. If they aren't done, you may still have an imbalance even with the crank, etc balanced.

If the rings are all good you wouldn't need to balance the rods at this time, just doing the crank on it's own would be of some benefit, if it was in getting measured up etc. but they would probably need the block as well to measure end float etc.
Once you get into something like this it's only a little bit more $$$ to do this, then you should really do that, and it's only another 50 to do this and you really should. Next thing, new engine and $2500 you have fixed a stripped stud! Have a good think about where you are at and what your plans are. A balanced engine is a sweet thing and I highly recommend it, but a fresh & balanced engine, now that's real sweet! But it doesn't come cheap!

tha motor has been rebuilt mint under a year ago block bores were checked come up mint same with crank im picking only clearances were checked tho and nothing got balanced dont want to spend heaps this time round really probs just balance the new crank?

If I were your I'd dowel the flywheel onto the crank. You'll only have to drill a couple of holes, and buy some silver steel. (I use 5mm)
Although the end of the crankshaft is f-king hard. I Killed a few drill bits drilling into it.

yeah i think that would be the way to go for sure, never thought it would be an issue until now but even dirty old k series motors have doweld flywheels. How just this lock it into place any better tho? surly a hi-tensile bolt as the are has to be as strong as a stud if not stronger?

The original flywheel bolts would have been probably as strong as grade 8 ones anyway, with dowels you will have the high tensile bolts AND the dowels for strength.