Mission acomplished and easier than I thought. I was 'living with'  leaking spieder cracking on my muffler (probably poor winterizing on my part) for several years. Using large bath towels to soakupwater on extended motoring, finally got bad enough so that muffler replacement was no longer to be put off.  Calling Catalina Direct I found that 'orginal' mufflers no longer available. However a replacement made to orginal specs was available.....$650 (wow) ...... was told that mufflers may be available for less from other manufactures,  "...but do you want to take a chance on a non-Catalina product?" So purchased the Catalina muffler and it fit in the space perfectly. My initial apprihensions we put to rest on how ealily I was able to remove the old muffler, even with my sloppy remove the engine exhaust manifold as I thought I would have to attempts with fiberglassrepairs. I only had to cut (and then replace) the intake hose. I used a hair dryer to warm the exhaust hose and it came of relatively easily. I didn't have to remove the engine exhaust manifold as I thought I would have to do. As I said new muffler slipped right in even though it was round but had a flat base, no mounting holes but it was an easy effort to drill new ones. After hosed reattached with double clamps I ran a test for about 15 minutes, no leaks! To complete the project, since I had the bulkhead off, I decided to degrease the bilge and paint. Happy with the result andas soon as I paint Slowdance's bottom she'll be ready for Lake Michigan.