Hi Philp,
You are correct the hull were a little longer (56') if I remember right. Most were LCM(6)
conversions. But with the Monitor & "Zippos" you need to build a Bow so the added length is an easier verture. I just bought the Dragon Kit which is fine for the conversion. ( Waterline Hull).. I spent some time on a "Tango Boat" ( ATC) These were of mixed origin. A few were LCM 3s but most were 5s and 6s. Every variation and manner imaginable.. Some with Re bar ( Grenade Screens) some with out and some with sandbags for added protection to upper hulls. I was aboard when we handed ours over to the RVN in 70.
Try this site for added photos and reference
http://www.rivervet.com/boats.htm .
Be Well/DBF
Walt