About 8 years ago I paid around $350 to have a local shop install new guides and seals, but I had to source the guides and seals for them. The valve seats were fine and the original valves were fine. They also pressure checked and checked for flat and fixed a broken exhaust stud.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC