I've used the adjustable Garhauer fairlead blocks with success and with great satisfaction.
Only downside is that the block is a single sheeve ... which is unlike the VEE blocks from
harken, etc. that allow you to run a (second) lazy sheet through the same block.
Garhauer has great products & service, etc. but IF you need any 'custom' made parts (tracks that need to be bowed/rolled, or otherwise specially formed .... send a TEMPLATE of the mating part and NOT send any calculations of arcs, etc. ; and then, expect to WAIT a long time for the delivery (as you do with most 'custom' formed parts, etc.).