Please help identify engine from photos
 

I just purchased a 1968 911 and it does not run well. I would like to know what engine I have before I start troubleshooting. The case is un-numbered and I assume it's a replacement case. I have these photos of the pistons/cylinders and heads from the previous owner. Can anyone identify the pistons and cylinder heads? Are these 2.0L 911?
Thanks,
Brent

http://forums.pelicanparts.com/uploa...1194683977.jpg
http://forums.pelicanparts.com/uploa...1194684024.jpg

That looks like a sand-cast aluminium case & early 2.0 911 heads (valve sizes will be 39mm intake 35mm exhaust) - is that a '65 date code (looks like 3-65 ?) on the head(s) ?