Well I am not the most expert to answer this but I had a set of "461" heads and eventually sold them and rebuilt the infamous "882" heads for a rebuilt 350. Here is one of many sites that will allow you to estimate the compression ratio:

http://home.tampabay.rr.com/1bking/c...calculator.htm

As I recall, the 461 heads had a 58 cc combustion chamber which will really increase your compression ratio compared to the 76 cc chambers of the 882 heads. For me the C.R. was too high for pump gas although Tech1 will tell you that if you deck the block and keep the quench gap between the top of the piston (flat top) and the bottom of the head surface to between 0.040" to 0.060" you can run up to 10:1 on pump gas. However on a high mileage engine the slop in the pin bosses may be enough that you risk contact between the piston top and the bottom of the head. Standard head gaskets are about 0.039" but other thinner ones are available such as 0.020". The other thing to worry about is that the 327 heads had softer valve seats made to use with leaded gas while the later 350 882 heads have seats for use with unleaded gas. The softer valve seats will recede over time with heavy use, but maybe not very fast just cruising. The seats can be replaced. All in all with decking the block and keeping the quench at about 0.040" (assuming your piston pins are tight) you CAN use the 461 heads, but I went with the cheap and simple treatment of using the 882 heads and paid to have the exhaust ports cleaned up. The 882 heads apparently have reasonable intake ports but poor exhaust ports and several studies with 1.6 ratio rockers on only the exhaust valves and/or an improved exhaust system have shown that the 882 heads need help for the exhaust valves. I will try the 882 heads for a while as planed to only 75 cc and maybe go to aftermarket heads in the future. There are others on this site who can answer this better than I can but that's my 2 cents.

Don Shillady
Retired Scientist/teen rodder