apex or drx

Figure out which class your racing. That could make a difference.

The DRX is 39" wide with steel wheels. And hard sprung shocks. DRX is supposed to have softer shocks available by now.
You can't remove the cylinder head cover without pulling the motor. Unless maybe you pull all the cylinder studs out first. (Possibly). But you have to put it back together also.
That's how far back the rear a arms bolt on. Replacement Elkas won't fit thru the upper a arm due to it being to narrow for the spring. Fox shocks probably would fit.
There is also a new DRX replica with the watercooled version of the motor out from a different distributer. It is currently the single a arm model. But will change to the double a arm model soon.
It will have a similar exhaust to the drx, ATVA legal.

The Assco Pro MX comes in a 70cc, 90cc, 100cc version.
The 70cc engine will have a aluminum nikosil watercooled cylinder stock. A new axle for this year also. There are Bolt on AC Racing goodies available now.
There will be a high performance 90cc Aluminum Cylinder kit available in the following months available as an aftermarket item.
the Assco Pro Mx's are 43" to 44" wide, can't remember exactly.
Assco Comes with lightweight Aluminum Wheels from the factory with the correct racing tread in them already.
Both units come with 12 " front shocks, and roughly the 10.5 " shock in the rear.
Both units need a proper race prep and assembly before there would be any expectation of the race bred performance that lurks within.
Both units will require a better/more durable air filter then what is currently installed on them.
Assco is premix and recommends 100 octane, DRX is oil injected and does not have a 100 octane recommendation.
For our use eventually all of the race units eventually get shocks and a rear swingarm to change the Suspension leverage ratio.
So one is about a grand more than the other, but has a wider stance , lightweight rims and tires, watercooled engine.
Both are excellant for the price.
Both have triple disc brakes with the assco having a foot rear disc and the DRX a hand rear disc.
The DRX has aluminum in front holding the brakes together while the assco has the heavier steel version. Both work excellant.

I haven't talked about wheelbase or weight. So there will be differences there also.
Just my insight as I have had several of both in my shop as new sale, or race prep.
JMO
Billy Holt