Mark:

You will need to email the seller to see if the guides have been reamed or not. If they have been reamed to a standard size then your old valves may work - it depends on how much wear the valve stems have. Measuring the valve stems requires a micrometer. Perhaps the seller can also measure the guides, that is, if the seller has a micrometer. If the stems have little wear and the guides were reamed to a standard size, then you'll be OK. If the stems show wear, then the size of the stems will need to be subtracted from the guide's ID to see if they are still in spec. If the guides have been reamed, then measuring and matching valves to guides can be done to get the best fit. If the guides have not been reamed, then you can have a machine shop ream them to match a particular valve since the stems will probably have different diameters. M-B valve stem to guide clearances are tight, esp. when compared to Detroit engines. If everything checks out, then resurfacing the valves, if needed, and grinding the seats, if needed, followed by a lap job should do the trick.

Good Luck!
Tom

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America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.