Some of the IND 361 and 413's had steel top ring land inserts and the comp ratio is very low 7.5-8.0.Not sure the inserts would hold up well above 4500 rpm.While the heads would be a great addition,I think at least at set of light duty truck pistons would be in order.There are also issues with shrouding the valves with the small bore.You may need to notch them for extra clearance.

How far down the bores are the pistons?