I've still got the '76 18R that was rescued from a trip to a landfill in Utah back in 2003. (Still needs full restoration but it's just sittin quietly in storage behind my deckboat and makes a good platform to lay the towables on. :smile )
They are the same style as the GT/R 13, 14, 15, 16 and 20s that were produced in the 70s. Like the 20s the benefit is the 18s are big enough to safely hold decent sized fuel tank and any V-6 you have the cods to hang on the back of it. In fact I was told (and you can see by the swiss cheese holes in the transom) that my 18 originally had cable/pulley steering and twin tower of power Mercs hangin on it for circle racing "back inda day". Supposed hull weight when new was in the mid/upper 300# range.
The boat is pretty unique, I've never seen or heard mention of more than a couple still known to exist. The hull is big enough to put a lake/pleasure use type of interior in like the GT20 or what I personally liked the idea of, a front/rear bucket with twin loungers along eachside like XR2002. I don't think you'd want to put anymore than 4 people in the boat but I'd feel safe with that many if you didn't have a huge fuel tank and alot of offset with a heavy motor.
I haven't discussed rigging ideas/recommendations with Darris much tho. I only brought it up with him a few years ago at a rally and he recommended NOT seperating the topcap from the hull during the rebuild. (Tho I don't think you could properly do it WITHOUT seperating the hull.)
I think Keith Holden is the only 18 owner listed on the homepage and he got into the mid/upper 70s with one of his hopped up V-4 SLOMCs.
http://www.allisonowners.com/KeithHolden.html My idea for my rebuild changes daily, sometimes I think do the XR2002 kinda interior, hang a period correct inline 115/150 on it and let my boys play with it. Then on the other end of the spectrum I think put one 10 gallon tank in it, solo seat and hang a hopped up 15" ProMax or even a 260 on it and going for the insane. :twisted evil
You got any pics?
RA