building a drifting kart is both easy and complicated.
first you need to get an older racing kart frame the older the better.
Steve is right.
the original racing karts pre 1976 were designed to "rear steer" which is what drifters do.
Racing karters tend to use that function only a little since you also scrub speed.
but if you wanted to keep drifting its no real problem at all.
The tires also were different.
they don't have to be old just the Correct rubber compound.
modern kart tires are designed to 'stick" and are extremely soft,with rounded corners and wide.
they are exactly the wrong tire to use if you want a kart to slide in a corner.
Correct vintage racing tires are made differently.
they have square shoulders are NARROW and hard.
the kart frames are also different.
pre 1976 frames were made with straight dropped front axles.
the frames weren't all stiff as steve said but they flex differently.
Modern frames with the y shaped front axle are designed to flex so the inside Rear tire lifts in a corner.
pre 1976 racing frames were designed to lift the FRONt inside wheel.
Actually the very best frames for drifting would be the historic racing karts with the dead rear axle.
those karts were the so called one wheel peels because the engine is connected to just one wheel.
there were racers back in the day who would install dual engines and have a different throttle for each.
theyed put the hammer to the correct tire in the corner while lifting on the inside engine.
if you were to make a kart like that with sqaure hard tires like the chen shens or vintage racer's you'd have a machine that could do a serious job.
of course using a boat anchor of a four stroke would stop the fun so you'd need something in the way of a vintage racing two stroke too.
my finger is tired.
if you're interested enough to read more about this post this question on
Vintage Karts and i'll be happy to go further.
plus just about everybody there has experience and insight on that subject so you may get more than you want.
dave