New fan belt idler pulley wider groove

[Norwaycharger]

Is this a problem, or can i use it?
Bought a New pulley for my 70 GTX 440 w/ac, but the New one has a wider groove than the old one.
The seller said that mopar used different suppliers in the 60-70`s, therfore the difference.
New on left

 

[coloradodave]

The new pulley you received is designed for a wider belt (stating the obvious). I would return it and try to find a different supplier. The belt will ride too low in the pulley which will accelerate the wear. Good luck to you.