jib block on traveler

I was hoping that someone could tell me what Harken or similar blocks I could use to replace the ones on the jib sheet cars. The pulleys have deteriorated to little jaagged pieces of plastic that make it hard to pull the sheet.
I don't want to have to replace the entire block/car assembly; I just want to replace the block part if that is possible.

I was also thinking of going to a 1/4" jib sheet so I was going to replace the jib clew blocks with the Harken 224's so the jib sheet blocks would probably need to be for 1/4" line as well.

Thanks

I had exactly the same problem with my boat, the rollers were shot. I'm using harken 341's now



but with new cars... the original assembly on my boat (which I believe is an 84), would have require the cutting/grinding off of the old block first, and even then I wasn't sure if the block would fit quite right... it probably depends what your cars themselves look like.

A 167 would probably be the same difference: