Im ready to make the switch to 4 stroke..Couple q's..

The HS142 has more low RPM torque.
I still have to pedal assist my EZM up the steep hill I live on and I have a 60t rear sprocket on it too.

My Chinagirl has a faster top speed than my EZM but it climbs the hill slower.
My EZM has waaay less vibration than my Chinagirl.
The HF79 has more hill climbing torque than the HS142. I am considering using one for my next build, home made jack shaft and all.
The Grubee 4G is good, but during my one and only group ride I noticed that my EZM out climbed the hills compared to the other bikes equipped with the 4G's. Back then it had the original 56 tooth rear sprocket too.
The Qmatic clutch is stouter than the 4G clutch. The 4G clutch can be easily improved though with either a genuine Oilite bushing or the ball bearing conversion if you get the Bicycle-Engines dot com kit with the long shaft engine.

I would consider a shift kit. My bike's low gear combined with 5 to 1 4G and the 28 tooth sprocket on the crank makes my bike so low geared I feel like it'll climb stairs.