No, the mounting screws are different, it will not fit the 98. There is a 98/USarmy cyclone feed made that will fit.
The cyclone feed increases the rate of fire on the 98 by using excess co2 to spin more balls into the chamber than is possible with a gravity hopper.
No, only a Tippmann A-5 comes with a cyclone feed standard. However a Cyclone can be purchased that will fit the 98 Custom.
It is cheaper to get the A5 then the 98 with Cyclone. They will be identical otherwise, except for looks.
It depends on the mods you put on it (if any). If it still has all stock parts (no mods) then a 5 dollar hopper is fine as long as it's sturdy. If you put a anything on it to increase the bps (fire rate) such as an e-trigger or a WAS board, then you may want to find a good battery operated cyclone feed hopper.
No, the screw set is off and there is holes for the cyclone feed.
If your 98 has a Cyclone Feed System, then it should work just fine. If you don't have one, you can buy the feed system and upgrade your marker. Relate link:
the barrel, hopper, stock, and many others.
No. the cyclone feed should tap into the gas line already built in for a response trigger. you should be fine.
As long as the hopper has the standard .68 attachment and the marker also has the standard .68 feeder elbow. So if the hopper fits on the marker your good to go.
No. they have two different receivers.
Yes, as long as it has two holes for the banjo hoses.
Yes, the tippmann 98 and the tippmann custom are the same marker, therefore the threading of the barrel will be the same.