holy crap, too many questions
ok, firstly 2.85 heads no idea, never seen one .... but the size of the motor is differences in the block not the head .. its probably got different sized chambers and thats about it.
179/186 have the pressed in studs and they are adjustable, uses different rockers to 202.
black efi head is correct, its almost the same as blue head as far as that goes, however the black efi head is said to flow better than blue/black carby heads in stock form.
the v6 rockers i have used are from series 2 vn/vp commodores, vn s1 are different as are VR onwards.
left is v6 rocker and pivot, right is holden 6 rocker, as you can see very similar dimensions, v6 rocker is thicker material though (stronger is good
)
right is the rocker as it comes off the V6, left is the modified version. fairly simply you have to cut the base off the pivot so you can screw it up and down on the screw in studs.
to get the geometery right (rocker center line on the right angle to the valve tip only required cutting of the pivot base (as above) and changing the pushrod length.
here you can see the left hand pushrod is a 202 length, the one on the right is from a 308 holden, just happens to work out perfect length to use with the V6 rockers.
thats about all there is too it. the main reason i did this is because my head has been running for years with standard 202 rockers on the screw in studs, and it used yella terra pivots which does away with the normal 202 saddles, problem with these as i found out when swapping the head onto a new motor was that they are alloy and obviously from the 200,000km odd they'd already done alot of them were broken through the center of the stud hole.
if you draw a horizontal line through the center of that bolt hole on that pivot thats where it broke.
yella terra no longer sells them and theres no other option that i could find to fit the 3/8 screw in studs and i wasn't keen to spend $400 on a set of roller rockers.
so $50 for a set of hardened 308 pushrods, a bit of grinding of the pivot bases and some time and she was all sorted. also the v6 pivot doesn't fit into the 202 rockers as the hole in the bottom is different shape and the pivot isn't a perfect fit inside it anyways.
oh and with the v6 rockers, they are 1.65 ratio where as the holden 6 rockers are 1.5 ratio, so thats a nice bonus to
now to the springs .... i have no idea what springs are in my head, dad setup the head before i got it, but i know from a mates head i compared the new springs he got to stock v6 springs and they are the same free height, coil thickness is the same and effectively it would mean you will get a stiffer spring on a holden 6 head if you used the v6 springs ... however i'd suggest you get a professional to ensure everything is ok before using them as they may be too stiff for your application and thats a waste of power!