I got the pushrods, lifters, etc... from patricks. You should check ebay, try 'chev 261' and see what you find.
The springs will depend a little on how radical of a cam you've got- The cam manufacturer will tell you how much spring pressure you need- Too little and you can have trouble. A mild cam can use stock springs, but anything with lots of lift will need stiffer valve springs.
I milled the head 50 and decked the block as much to increase compression. Then I checked valve clearance with the pistons and it was okay.
I had the valve seats replaced with hardened seats to run unleaded.
I tapped the front bearing cap to be able to install the two bolts from outside the timing cover rather than having to pull the oilpan to remove the front motor mount to change the cam.
I set mine up for a remote spin on oil filter- If your 261 is not set up for full flow filtration, it can easily be converted while you still have it apart.
http://www.speedprint.com/Deves50/oilfilterinstall.php HEI igntion/12 v conversion/dual exhaust/upgraded intake and carb, etc...
As far as the carbs go, I'm using the offenhauser dual intake with carter=webber progressive two barrel carbs. Next time I'll probably use Cliffords intake and a small progressive 4 barrel just to have one less carb, and the dual linkage, to deal with.
