273 commando cylinder head bolt torque specs ? same as 340 ?

Torque on a fastener cannot be calculated. It is an attempt to get a desired stretch on a blind fastener. It is found by trial and error, and is also dependent on the lubrication. See posts #14 and #19 and take it to the bank. Perfacar also is giving you which head gasket to use. The most accurate way to "stretch" a fastener, say a rod bolt is to measure before and after torquing to achieve the desired range of stretch.