Last year I reworked a set of older Indy SR's.
These were probably about 1998 vintage or so. The early ones had more of a "D" shaped chamber. The newer ones have the heart shaped chamber.
The newer chamber is cast with more space around the valve adjacent to the chamber wall.
The early ones had noticeably weaker low/mid-lift flow with the valves being more shrouded by the chambers.

I have only a couple pics, and not any good pics of the complete OOTB chamber shape.

The early heads also had quite a bit more meat that needed to be cut out of the bowls, as well as having a pretty chunky guide boss.

They can end up as good as the newer version, it just take more work to get them there.

The first pic is after the valve seats were cut along with a chamber relief cut.
You can see the extra material under the seat and the guide boss that will be getting trimmed away.

The ootb flow numbers aren't really that good at all, and aren't any better than a half way decent ported 906 until over .550 lift, and the low/mid-lift flow is way down compared to even a mild bowl blended stock head.

These are the kinds of heads where if you just ran them ootb, you were likely going to be disappointed.

Tested on a 4.375 bore, 28" pressure, radius plate on intake.
OOTB test is std port, ported test is MW size opening.

A- OOTB
B- ported

Intake:
Lift------A/B
.100---69.0/73.1
.200--124.9/146.4
.300--173.2/209.8
.400--218.0/260.8
.500--255.9/310.7
.550--268.3/326.9
.600--274.8/336.4
.650--278.5/342.0
.700--281.6/347.7
.750--283.5/353.4
.800--284.2/359.1

Exhaust:
Lift------A/B
.100---52.8/ 57.2
.200-- 89.2/111.6
.300--127.7/162.4
.400--162.4/205.8
.500--187.2/236.8
.550--196.7/248.3
.600--203.2/252.1
.650--206.2/256.7
.700--208.1/261.6
.750--210.8/266.2
.800--212.7/268.1