what parts do I need to convert a 300 savage 99 to 243 win

Sell the 300 and buy a 243.
What model is the 300? Depending on what it is you may be real money ahead to just sell.
Not being snide just to tired to get in-depth. Someone will be along

I’d keep the 300 and buy a 243. Check the SAAMI #’s for each....

To be a .243 candidate, the action needs to be serial number 900,000 or higher (length issues). In any cartridge conversion on a 99, you may have to replace or alter the rotor and cartridge guide and possibly alter the feed ramp.

...plus a barrel and labor.

Didn't someone here recently say length of the action had not changed.

When they went to 900,000 serial numbers? The receivers didn't change length, but the internals did change. Rearranged to allow longer cartridges to fit inside. Loggah and family redid one pre-900,000 99 to handle the 308 family of cartridges, but it was a LOT of work according to him.

So the newer rotor will not fit in a pre 900K rifle? I remenber Don's picture of the 358 winchester they did also remember he said it was a pain with much work.

Maybe what I am missing is the internal work or length. Any 800k rifles inj the 308 win family?

No, a 900,000+ rotor won't fit into an earlier 99. And the 800,000 rifles were all 250-3000/300 and the internals identical to the rest of the pre-900,000 rifles as far as we know.

Thanks that’s what I wanted to know