2 points,

1. as far as i know, you were right when you said the lifter is angled over in uk heads so machining would be required to fit roller lifters, also there's tonnes of roller lifters available for american V8 engines so there is surely a way of fitting them.

2. in my book "How to build, modify & power tune CYLINDER HEADS" it says that on turbocharged engines it is best to leave the exhaust ports rough like the inlets, as this promotes a build up of carbon around the port (only very thin mind) that acts as a thermal coating like a ceramic coating keeping the heat in and promoting a faster spool up of any turbo.

i'll scan some pics of the book as there's a section on porting a CVH, i'll make em high res so you can read em on here.

JOSH