That D15BX bottom end has a crank that's probably good until about, what, 7,000 RPMs? I think, possibly, less. I thought the Z6 factory crank only spun till 7,200 RPMs before it's life was no longer guaranteed, and the Z6 block (among the A6) is one of the only good D-Series blocks around.
1.5L is your first problem. Tiny cylinders aren't going to produce you any torque, all that block is going to do for you is maybe give you a little more compression than a stock complete version of whatever your friend's head is from. Immediately, you would need to tune it, not to mention worry about stuff like piston\valve clearance, mileage, etc...
Your friend has a spare head. Do you know how he's been taking care of it? The gasket surface needs to be pristine for a good seal, for one, if he pulled it off and sat it on something dirty, hard, or unfit for the head to be sitting on, you could have problems with your swap right off of the bat. When buying used engine components, consider what kind of care they need once they've been disassembled and find out if that's the kind of care that's been taken of them since they've been away from an engine.
If you are going to do a mini-me engine, here are my base, non detailed recommendations for you:
block - head
a6 z6
a6 y8
z6 y8
d15bx y8
My favorite mini me uses an A6 bottom end and a Y8 intake manifold, as for component comparison, I believe those to are the best in their respective categories from the factory. The A1\ZC pistons are ridiculous for high compression\NA setups, A6 pistons make for more compression as well (but not as much), Z6 and Y8 pistons generally lower it, A1\ZC rods are I believe the strongest, the Z6 I think might have the best crank (I don't know the D-Series cranks as well as I'd like to).
The D15B is a great engine if you insist on a 1.5L SOHC VTEC power-plant. It's SUPPOSED to be the way it is, thus eliminating all of the Frank-issues right away. Secondly, it's factory OBD1 (schwing!) and third, it's fairly cheap. 3 Stage VTEC is also a cool factor (although, I never really quite learned what the hell that even MEANS when I was in Honda PACT, lol) if it actually DOES anything more than regular VTEC (obviously it whips vtec-e) and it's certainly nothing to even bother with comparing it to i-vtec.
IME, 1.5s are trash, just my .02