l am woundering if the aluminium upper+lower arms on the kyosho MP7.5 INFERNO GT fits onto a Hobao Hyper 8? they roughly look similar.
Aren't you trying to get your hyper 8 to as high a speed as possible. If so then why would you want to put on some aluminium arms which are heavier than stock?
Even disregarding the weight difference, plastic arms flex and return to shape, and if they do break they are cheap to replace. Aluminum arms are expensive (relatively). They will bend and they stay bent, very difficult to straighten back out properly, and they will be weakened.
When I first got into the hobby I thought aluminum always = better, but quickly learned that the stock parts are plastic for a reason. There are certain exceptions (like UE stuff) but those are made of higher quality alloy and built for abuse (and the price reflects that). The only alloy Inferno arms I've seen were cheap "Integy" type of alloys that will almost surely bend like soft butter.
As far as the IGT universals I can't say what will fit. For the center I think regular dogbones are fine, since the angle stays constant (I use small pieces of fuel tubing to keep the dogbones centered and cushioned in the cups). Some people have told me you really only need CVDs in the front, but I run front and rear.