How will 15x6.5 with a +38mm offset fit under stock guards and stock suspension of a datsun 1200 ute im guessing ill need like 15mm spacers front and back?

I think it might fit without spacers.

15mm spacers would bring the offset back +30, which is the original 1200 wheel offset. But there is maybe 25mm extra room each side. It largely depends on the tire size you will be fitting.

Front


Face measure: 109 mm (4.3 inch)
Back measure: 89 mm (3.5 inch)
Total well width: 198mm


Rear


Ute Face measure: 75 mm
Ute Back measure: 140 mm (5-1/2 inch)

what size tire would you recommend with a low tire wall and a little bit of stretch?? would they be flush with the guards??

Based on the various wheels I have and the measurements of two 1200s, I think that 6.5" wheel +44 offset will not be flush with the side of the car. But might be inside the body edge by about 15-25mm thus clearing the inner fender lip (note there is about 10mm variance in different 1200s from side to side). 1200s can take a 7.5" wheel and still be flush to the body side.

6.5" wheel is for 185 or wider tires normally. So stretch would mean a narrower tire than this. What about 175/65R15? You will lose some traction compared to the 185/60R15, but might look slightly stretched.

I'd recommend test fitting the wheel in question to be sure how it will look, before buying. Or create a mockup using cardboard and a stockie.

Here's a virtual mockup based on 220 mm wheel well. You can double-check these measurements on your ute.

It shows that a 6.5 +44 wheel might be touching the spring. So a minimum of 5mm spacer is needed. 15mm spacer might get it close to to flush with body side and have 15mm clearance to the spring.




With flush 6.5 wheel, then the question is which tire width would clear the inner fender ... obviously stretched narrower will be required.

6.5 inch wheels need +20 to +16 to fit properly, you will need 25mm spacers, thats not to rub on the suspension at the front. any more negative then that and you will be rubbing the front guards.

The rear will work with +25 to +15ish.

So i will definitely need spacers?? will the wheel studs be long enough if i need 25mm spacers??

Yes. How much spacer is for you to decide. Get out and measure your ute, compare the measurements to the graphics above.

* I estimate a +5 spacer is required for +44 6.5" wide wheels for an average 1200. Or if you want to get them flush to bodyside (which means the tire rubbing will occur), +15 will be closer.
* townie says "6.5 inch wheels need +20 to +16 to fit properly"

Of course it depends on the offset of the wheels, and the side-to-side tolerance of a 1200, which has been reported up to 10mm difference on different stock 1200s.

dd, my opinion is from my car, which the wheel rubs the strut unless its under +20, that was with 6.5 inch watanabe's and 280zx struts.

i have all stock suspension so wont i have more room with the standard struts?