I really doubt anyone is going to run displacement tests on cars in stock eliminators.
All sorts of fun stuff you can get away with long as it all looks stock.
garret turbo machined to accept some big wheels in disguise, ported heads with big valves, cams, ported 2 piece intake, ported exhaust mani, ported 2.5" swingvalve. If you have to run stock injectors, have them rebuilt for MUCH higher flow. Find a way to sneak alky into your intake. Dynotuned in a stock looking ECU box.
As Ive learned in my reading, there are the rules, and then there is the reality of what everyone is doing at the track. If there was limited boost, you would find people cheating on all their boost reference points, etc, or running a little cheater gas (nitropropane).