how close does the weight of the conrods need to be?
I have weighed mine and 2 are about 620 grams and the other 2 are 619grams. My scales only go down to 1 gram is that ok or do i need some that are a bit finer.

 

Thats usual mate. Dont worry about 1g.

Match them to your bearings, and piston assys and chnage them about so the complete assys are as close as possible.

 

I've had three sets out of three different EJ20 lumps and in every case they are matched within a range of 2 grams at most. Can't remember exactly what they were, but the set I've got in the garage all came in around 625 I think.