Odd Size Rims on 68 c10.

[socalkevin68]

Need some help please...i just bought my 68 c10 a few weeks ago. It had 16" 6 lug newer chevy truck rims and big tires on it...I just bought new 6 lug rally rims to put on to bring it down some...well when i went to take off the rrims..i noticed the lug studs say M on them (metric I assume)..I know for a fact my last 68 c10 had regular 1/2 studs on it...
The metric studs that are on it now are bigger in diamter than the 1/2 " that should be on there...
I tried one of my rally tims and it went on..but when i put the metric nut on it didnt seem to fit quite rite....like the taper was too small on the rim for the bigger nut..
What should I do..I really want the new rallyrims on my truck...If i pop out the bigger metric studs will the correct 1/2" studs go in..or did they drill it out to make it bigger?
very confused ..as i've never ran into this b4..
thx for any help..its much appreciatedl