I have a csb 350 1990 with comp cam 08-503-8 and I think the engine has a rod bearing that is bad, the knocking comes from the bottom. I'm planning to buy a 383 short block, but a short block from 86 or newer with 1 pc seal is kind of hard to find here where I live but theres lots of 2 pc seal short blocks for sale, so my questions are: Can I buy an older short block and use my comp cam and just buy new lifters that fits the older block and cover the hole for the fuel pump or is it some more things that will not match?

ok ok, there has been exactly ONE person i've ever heard ever say they had a "CSB", and if it's you, then this is the SECOND time i'll say - it's not a CSB - it's an SBC - small block chevrolet. It's the naming convention. It removes confustion.

Typically if you want to use an older 2pc RMS block and a roller cam, you need to use a "retrofit" roller cam. I'm not wise to this conversion, but what I *think* the difference is;
- retrofit has a fuel pump lobe (not a big deal to you)
- retrofit cam has a slightly different cam nose setup, to hold it in the block. I was never clear on this. Perhaps do a search on retro-fit roller cams and see what they say
- yes, if you're using an electric fuel pump, you can just use a blockoff plate.
- you would need retrofit roller lifters, which are connected to each other with dog bones. These cost about $500 a set.

Re-consider finding a 1pc rms block, or -- why not just machine your existing block? Are you trying to avoid the downtime?

I'm sorry but in Sweden we start with the Chevrolet and then the type, Small block and yes it was probably me the first time :-)
The season starts right now here in sweden and I want to use my car, and soon the holidays start here and then it will be a pita to find any1 to fix it. So I thought it would be the fastest way for me to just buy a 2pc block, but they often use a 110 lsa cam shaft and what I reed it seems kind of difficult to map it so I would like to use my comp cam insteed. But if its not possible I'll buy a retro then.

Map it? As in you're running EFI? If that's the case, yes the tighter lobe seperations *can* be pickier to tune for and generally the wider LSA gets recommended (114°).

Factory roller can go into an older block if you fashion up some kind of spacer and use a late-model timing set and a thrust button. Obviously retro rollers would be required.