Can I add Myson radiators to an existing Cast Iron system?

I am rehabbing a home and the bank did not winterized the house properly, about 1/2 of the cast iron radiators have cracked tubes.

The supply lines looks good, so my question is, can I swap out the cracked radiators with a modern style, like a Myson? The supply line is 1" and Myson and others requires 3/4" and the radiators run in series.

I assume this will restrict the flow to the older radiators, but will it have a noticeable effect ?

Thanks in advanced!