"...I wondered, what is your feeling over the years, are the RA2 & RA4 about the same power or is one stronger (in the same weight car!)?"
The RA4 has to make more power, for the reasons mentioned. Bigger cam, because of the 1.65 rockers. RA4 heads are said to flow a little better. Other than that & the alum intake, as far as I can see, for all practical purposes, the engines are identical.
I'd guess the RA4 would have to make at least 15-20 more hp, just because of the 1.65 rockers. May not be that much.
In 2013, the RA2 Bird engine with auto trans was defactored down to 340hp, which makes it very competitive. That's only 7hp more than the 330hp D-port engine's NHRA 333hp factor.
http://www.classracerinfo.com/Engine...3&MAKE=Pontiac
The '69 RA4 Bird engine has been 356hp, since 2007. That also seems very fair to me. But not many Pontiac guys are willing to run a set of RA4 heads on a race car. They are rare & worth lots of $$$$$. Bruce Noland now has a '69 T/A tribute Bird with the RA4 engine. He's got it down in the mid 10's, so far.
http://www.classracerinfo.com/Engine...2&MAKE=Pontiac
Several guys have run quicker with RA2 Birds. But, I figure that's mostly just because the heads have been cheaper, so lots more guys have run 'em & have had years now to improve the performance.
The main reason I'm pretty sure the RA4 makes more power is because Scott Burton's '70 RA4 powered Bird was the quickest Pontiac powered Stocker ever, running real low 10's & even dipping into the 9's, in Stock legal form, but not in Stock competition. If any legal Pontiac Stocker has run quicker, I'm not aware of it.
John Schloe ran a '69 Bird with RA4 power, but ruined a head & switched over to a D-port combo.
One more thing is that although there have been quite a few '68 Super Stock Birds, John Angeles' '69 RA4 SS Bird was the first reg SS class 400 Pontiac powered car to dip into the 9's. Keri Angeles did that back in 2000. It has run in the 9.80's since that time. Don't know if any '68 SS Bird has run in the 9's or not. They're certainly capable of it, since several guys have run low 10's with '68 Bird Stockers. I suppose nobody has really tried to run 9's with a '68 SS Bird. Right now, I can't think of a single '68 Bird running reg Super Stock. Mike McKinney ran one for quite a while. Don't know it's quickest time. Marty Mckinney has it now, but painted orange.
https://www.facebook.com/mckinneymarty88
One new wrinkle which has come along in recent years is that now, you can use Edelbrock #60587 alum heads on the RA4 engines, in Super Stock.
http://www.classracerinfo.com/Engine...2&MAKE=Pontiac
Don't know the current price for those heads. But I figure it is several thousand cheaper than original unported RA4 iron heads. The NHRA hp factor is 350hp. Don't know of anybody running that combo, unless the Angeles Bird is running the Edel heads. The 428 Pontiac engine, with the same Edel heads is more competitive @ 330hp, & is being run in several GT cars. But, this is the Stockers thread, so that's all I'll say about SS, here, for now.
http://www.classracerinfo.com/Engine...9&MAKE=Pontiac