The ca16/18 are actually lighter than the 4age due to having no skirt on the base of the block.

I would suggest the bigger bore ca18de 83mm vs 78mm for the ca16de.
Then destroke 10mm using the crankpins so the rod mains will be 38mm
(like sportbikes) and 83.9mm will end up 73.6mm getting you 1593cc.

The custom conrods would cost around $1200
but ca18de are found everywhere cheaply in junkyards.

Steve Newing made 230-240hp from his worked ca18de so if you can get
him to work on your ca18de head Im sure hed find a way to make close
to those numbers at higer rpm.