I think Warren must have modified the strut angle and shaft log in order to accomodate a prop that size (29") (see picture below). At first I was thinking that the 29" must be the pitch but heck - I don't know now. I spoke with and emailed Warren several times when we were both working on repower/refits ( I think he communicated with Paul and several others too). I will look for some of the email details to see if he discussed shaft size etc.
Here is a link to Warren's photos that his son Darren put together.
http://www.flickr.com/photos/chriscraft/sets/
My knowledge of the 38 is limited, but I did do some research to check blade tip clearance to see what props the 454 groups were running before putting 8.1L Crusaders in my 35. Seemed to me that a Stock 38 could not fit a 29" blade as configured from the factory. The biggest I found was a 24" diameter prop and they was above the recommended 15% blade tip clearance (with no apparent problem from what I hear).
So keep in mind if you repower, you need a blade tip clearance of 15% of the prop diameter (historical rule of thumb) and you likely will need the newere X series props. This is a more highly skewed wheel which can accomodate the higher torque engines today and will allow for a pitch far in excess of Square (diamter = pitch).
My initial repower plan was to put Cummins QSB 380HP (common rail diesels) motors in my 35 as I do have a bad case of diesel envy and wanted those engines something bad. Warren helped me decide against it by discussing his required modifications. As most know, the Gasoline boat thing is an American anomoly. We are about the only folks not running 100% diesel for inboard applications. Aside from adding another 15-20K over the Gas Crusader expense, I discussed the custom engine vents that Warren had made for Bambi. Quite honestly I didn't like the idea and didn't feel competent to do a baffle air intake like his and I know that while I am a pretty good glass guy, I didn't have the ability to make a vent system that wouldn't ruin the look of my hull. The air requirements of a modern diesel (or any diesel) are significant and it needs adequate cooling so as not to allow heat build up that will rob horsepower fast. The torgue is typically around 900ft/lbs at 2000Rpm for that Cummins QSB 5.9 liter diesel. That is some real rotational force and would command a shaft diameter of probably 1.75" (on the small size)-2.25".
HEre is a link to Warren's shaft and strut photos (pretty nice stuff - huh?):
http://www.flickr.com/photos/chriscraft/247427985/in/set-72157594291005981/
Best regards,
Greg Gajcak
35 Commander
Chicago, IL