All the aftermarket are a lot better than Stock L92's so we can agree on that. Cathedral style heads are just as good but to a point of........ over .700 lift and that"s when LS7 style heads come into play for larger engine's that require more air and they have more potential for Better intake set ups aka: FAST Intake. Now here are the top LS3 heads manufacturers TSP, TFS , and ole MAST =....Which would.........more than likely be the Winner in LS3 style head comparison:

MAST: Rectangular Port LS3 11 Degree 4.000"-4.070"

Flow Data w/4.000" Bore Plate
Lift Intake Exhaust
0.100 74 61
0.200 146 119
0.300 222 188
0.400 282 219
0.500 330 236
0.600 360 251
0.700 372 260

•TSP LS3 255cc Runners

Lift Intake Flow Exhaust Flow
.200" 157 cfm 117 cfm
.300" 224 cfm 170 cfm
.400" 281 cfm 205 cfm
.500" 329 cfm 225 cfm
.600" 358 cfm 235 cfm
.650" 366 cfm 240 cfm
.700" 369 cfm 243 cfm

TFS:255 LS3 heads/ Flow Data w/4.065" Bore Plate
Lift Intake Exhaust
0.100 71 59
0.200 146 113
0.300 231 171
0.400 294 215
0.500 334 240
0.600 363 252
0.700 382 258
All these heads would be from 5 to 20 hp diff at the max with same cam and intake setup there really is no need to compare, it now comes down to Preference and Budget and all these heads go for around $2500 bucks give or take 200.

 

Good info

 

Something to note:

Chamber cc

The more you mill tbe worse the flow gets (typically)

 

I personally like Mast heads and thinking 1 of these 3 will be the future heads for my 408-L92 I really don't need any parts (bare heads) AKA solid roller and i would have to pick my own springs but one of these will be BUTTERED UP = PORT WOrK by someone to put them together more than likely it's going to be Mr. Good. that some day is way off I want to get the combo together and see how good it all holds up mostly valve springs and then I will just take my valve train and put it on a aftermarket head .If you could find some photos of the July 2013 Popular Hot Rodding issue with the article:396 Chevy -LS Style those heads were a work of art I want to own a set of those.... I will own a set of those.......Future!!!!!

 

Also someone will say why would you have CnC'ed heads ported? 1. I hate to have something like everyone else I'm willing to spend some coin to get what I want. 2. CnC heads may be good but you can be rest assured that a Talented head porter can find some-more(CFM's and still keep great port Velocity) I would bet I could get 390 to 400 cfms with 4.070 bore on a flow bench. We do know that these heads(Stock TFS..etc after-market) would flow over 400 with a 4.125 bore or larger in stock CnC form.

 

From above: ALL TRUE! I like the Mast heads (they are the best heads to Me ) and I know G could work some Magic on them he will put them together might as well have him go through them as well. I understand everything you said. Head flow numbers are great for marketing, but do not tell the full story. There is a lot more to it. = CFM's and still keep great port Velocity without hogging out the runner)
I go to the track on Sundays @ at E.Mount Houston 1/8mi (Baytown 1/4mi and it's to far.) And what you said holds true at the track and street. It's all about the combo: trans, stall, car wt.,engine, rear gear, and most important can you get it to hook and get it dialed in.