You will find that this issue is not specific to Spica pulleys.
Of concern would be to ensure that the timing marks are correct for the engine irregardless of which pulley is used. One just can't swap pulleys and expect the timing marks to be correct.
For the waterpump, you can use a two port pump for a Euro 1750.
Papajam, Can I use this two port pump on a 2.0 liter from a mid 70's Spider as well?