RIO have a spey line selector table which can be used to find the right line for most commercial rods.
http://www.rioproducts.com/skin/summ...ine%20Recs.pdf
The best way is to find the "grain envelope" for the rod, and use the right grain line. The lower end is for kiss and go casts eg Scandi and the upper for sustained anchor ie Skagit/DS. Sometimes (ala Meiser rods) the upper grain limit includes the grain of the sinktip, normally up to 200 grains - This is not the case on the RIO doc, the upper grain is the grain of the Skagit line.
The RIO table also has a column for RIO Outbound lines for casting overhead, but are heavy lines.
Sometimes US weight numbers do not correspond to the UK numbers, which are normally higher. eg a Meiser 15' 7/8/9 is grain matched to a UK Carron 65' 9/10 line (~800grn).
What is required is a table listing grains for each manufacturer's lines, and also the grain envelope of each of the rod manufacturer's models.
I recently requested the Grain ratings of lines from Carron, and they happily provided them.