Yea, you can just replace the 4 lifters but be sure to break them in same as a new camshaft. If you have the newer main seal with out the "feet" you could loosen all the mains and remove the main cap and push the seal out, besure you lube the seal edge with oil and use loctite #518 flange sealant were the steel main cap meets the iron part of the block.
Harry
PS I just thought the "feet" are on the cap of the early engines so should work on anyone.
