Welcome to Swedespeed, Andrew.Just bought a 1975 164E in South Africa and all the bushes are really shot. I can find all the bushes online even poly but not the front upper which I have now found out are different than the 140 uppers.
Here are the Volvo Part Numbers associated with 164 A-frame bushes...I emailed Voluparts and the upper bushes for the 164 are no longer available. http://global.gcp.se/ and http://www.skandix.de/en/ both shows the part as out of stock. Voluparts also suggest changing the upper A arms to 140. One wonders why Volvo changed just the upper arms / bushes and not anything else. All the other components lower arms and all the ball joints are the same and yes the 3 litre is heavier. At least this way I can have poly bushes all over. Just need to decide on SuperFlex or SuperPro. The car is actually in very good condition for the age but still needs plenty work and suspension is first.