I did think that was kind of odd and that is the reason they are direct copy's of the Dart's. My 200 platinum's use a 1206 also that were never ported. I did put a 1205 on the new head and noticed it was off at the top of the port, you can open them up on the roof even more but then one would...
I did some port checking tonight. the Dart copy at the pinch was .925 wide and the Iron Dart was 1.05 almost 1/8 of an inch more on the Darts. Now wonder the copies don't do as well power wise, I will need to fix that.
The new Dart copy heads came in today. Overall they look pretty good for $386 bucks, it's funny the only area that needs to really be fixed is the pinch opening at the port entrance. These heads use a 1206 gasket but all the side walls and center port divider need a lot of work but being they...
I painted my new garage floor back in 2006 with Rust-Oleum and it's been pretty good, but I think now in 2022 there are better coating alternatives. I have a few spots that lifted and the paint scratches easy but it was better than bare concrete.
Base your plugs by the fire ring at the base of the porcelain it should be a light grey. Look for the color change on the plug strap you should see a color change at the bend of the strap then you know the timing is right. Pulling a BBC with 3/8" heavy valves can have problems in the high RPM...
The 2004r and turbo 400 share the same spot, so what I did was moved the crossmember back made side brackets on my 2nd gen to put the turbo 400 in the car. Has worked great for over 30 years.
One thing to not over look is valve float like G72Zed said, it will make you chase your tail diagnosing the problem. So if after changing external stuff, like carburetors, plugs, wires and ign stuff then you will need to take a look at internal components.