I'd maybe venture into the 301cc or 420cc engines for a bit more power for a full suspension kart for a grown adult.
If your doing double a-arm suspension in the front you'll want 12 heim joints. If you want to go with single a arm, then you'll only need 4 heim joints.
Rear suspension you have a lot of choices for design and that part is really up to you. You can go with the standard swing arm and you can either mount the engine on the swing arm, or if you can match the pivot of the swing arm with the sprocket and chain from the engine, you could mount the engine on the kart frame itself.
Another option is run trailing arms instead and either have sprockets on each arm, or you could get 4 sets of U-joints for 1" axles with a 1/4" key and have independent suspenion. Then you'll need really just 2 heim joints unless you want more.
Another option is similar to the trailing arm in how many u-joints, you could run double a-arms, then you'll also need 16 heim joints for those.
Or you could run single a-arm and just use 4 heim joints and 2 u-joints.
Just a heads up, trying to get u-joints to line up with the pivot of the suspension is going to be a bit of a pain, but it'll be well worth the effort.
Additionally you'll need shocks, either air or spring.
Building a full suspension kart or mini buggy is not a cheap endeavor. It could be more than double the cost easily of just a standard yard kart. So once you decide on which kind of suspension you want, I highly suggest you buy parts a little at a time and not buy them all at once. Get a small collection of hardware because it's always the small stuff that adds up fast, not the big stuff.
. ive been looking into the cost of my next ride and want a little more suspension in it. the go kart i use i did not build myself. only restored it. i was wondering how to go about making the pivot in the suspension arms and what materials to get so i can factor it into my budget. thx!