[Brian]

pros and cons;
Aluminum heads are original to your engine
Aluminum heads are higher compression
Aluminum heads require far more care in fitting and in use; need to be fitted with non copper head gaskets, anti seize applied to all studs to prevent galvanic corrosion, additives to coolant to prevent the same...
Also care needs to be taken fitting spark plugs; use more anti seize!


Cast iron heads expand/contract at same rate as the block.

Cast iron heads are quieter.

Although they are lower compression, because they hold the heat more than ali, the 'effective' compression is much the same.
So, all round they are less worry...


Strange you've found the cast iron rh head to be cracked...my experience is that the lh heads seem to be the ones that crack for some reason?



Take your pick....