Does the one from the LA fit the same mounting holes?

Does the one from the LA fit the same mounting holes?

    If you modify the engine, my previous advice is null and void.

    Brett

The engine is and will remain stock.

I don’t have a muffler for it. Should I get one, or use open exhaust?

What is wrong with a tongue muffler?

  Not running the supplied parts is a modification, at random. A random modification makes it impossible to predict the results, and, doesn't correspond to the configuration we ran, so it's not likely to be the same. So the advice/information I have is no longer valid.

 
  In absolutely every case I have ever had where someone complained that their engine didn't seem to run like mine (implying that I didn't know what I was talking about), I eventually found out that they ran it "stock", "as recommended", except that they replaced the spraybar, changed the venturi to match "the chart", added head gaskets, and/or threw away the muffler because it was "too heavy". In all of those cases, restoring the engine (where possible) restored the original, far superior, performance. "Oh, I guess that really does work..."

  I have run various engines (not the 15FP, but all the others) with various erzatz parts, and always ended up with the stock parts.

   That is why the advice from above is void if you start modifying the system.

    Brett

p.s. https://www.ebay.com/itm/O-S-10-15-FP-LA15-CZ-M-MX-MUFFLER-ASSY-NIP-871/223433422887?hash=item3405ab7827:g:YMIAAOSwhTBa57K0