Help me out with offsets on these JConcepts Choppers

[xlDooM]

So, I'm looking at these premount tires because I've heard great things about them (among others, in the budget rc video below):
http://www.jconcepts.net/shop/choppers-blue-compound-premounted-rear
http://www.jconcepts.net/shop/choppers-blue-compound-premounted-front

They are labelled "front" and "rear" because apparently many Traxxas vehicles have different length A-arms front and rear and the wheels have different offsets to make the footpring square again. However, which ones should I get for an ECX Amp? Are the Traxxas rear wheels the standard offset, or are the front standard offset and the rear ones narrower?

Here's the video where they came recommended (around 9 min mark):

 

[mikel81]

The different offset on traxxas vehicles is on the 2wd versions only. So you could use a full set for 4wd or two pair of either fronts or rears to have the same width. The fronts would be wider.

 

[xlDooM]

Alright, so the fronts are the odd ones out then, and for the Amp I should just get a set of 4 rears unless I want it to be sper wide. Thanks!