http://www.southernnational.net/Rules/2004FourCylinder.htmIn Puerto Rico the later pushrod version (3tc) is the choice of head for some and the 3tg twin plug head for others. After 78 the valve angles and port mods were inproved for high comp as in the latest hemi by dogge. With the less inclined valves used in the 3tc normal aspiration with high comp is no problem as in the fiat tc engines. The top turbo drag 3tcs can see 800hp and 7-8 seconds with turbo, nitros and alcohol of course.
The link above even shows a weight penalty when using the 3tc of 50lbs and 89mm bore and no other engine maker has that except when going over 2.2ltr.
These things have to race with less capacity than 2.2 engines from other companies, carry more weight and so on.. so they cant be that bad.
As for 2tgs making over 200hps is possible but yes the early hemi head might have probs with high comp. As for the 3tc with pushrods they even run at 13.1 compression and spin to almost 10000 rpm in american speedway.
The 4ag is the grandson of the 3tg.
Personally Ive had over 30 or so all up of 2tgs, 18rgs and all other kinds of Ts of different models and at over (twin cammers) 4000 rpm rocked but I still prefer the 3tcs simplicity.
Strangely it goes to show how little the twin cam version made as the 2tg with 40mm twin solexes (weber type) produced 125hp and the less equipped 3tc twin carb version which made 114hp from factory (with only 2 twin downdraft hitachis and less compression.)
I know which one Id have considering also the twin cam head almost cant be shaved at all except by a specialist for fear of piston valve inteferrence and the oil pressure switch for the chain tensioner cost over 350 australian dollars new and they often broke off if you bumped it with anything.
Considering whats available for the 3tc in the states It would make sense to go the choice he made.