Several people saw a white and green vehicle around Keddie, at the time of the murders.
This is variously described as a "Blazer", a "pickup", a "van"... Sorry if this is obvious stuff here, but I'm not familiar with cars in general so I did a bit of a search on the 'Blazer".
The Chevy Blazer was an early 4WD vehicle, which looked somewhat like a pickup (or 'ute' as we call them here) with a roof on the back. The pictures I found of Blazers from the 60's to the 80's show a vehicle that could easily be described as either a van or a pickup:
1969 Blazer: http://image.motortrend.com/f/35423943+ ... rtible.jpg
1988 Blazer: http://static.cargurus.com/images/site/ ... 35867.jpeg
1972 Blazer: http://www.davidhowardemery.com/wp-cont ... er-002.jpg
80's Blazer: http://farm3.static.flickr.com/2001/581 ... 4cec55.jpg
Here's a few mentions of vehicles which might match that description from the timeline. If I've missed any, please do add them below. I think collecting those statements might be useful.
Frank Davis
Moved from Keddie 4/1/81. Frank reported an argument between Sue and man in white and green Blazer on March 1.
Fred Downs
Saw a utility truck with NV plates leave Keddie via the lower road about the time of the murders
Arthur Jawad
Lived Keddie. Walked to the bar and then home @ 0100-0110 4/12/81. His pickup was parked in an 'unusual place'. Took a polygraph.
Seabolt, James Sr.:
Went wood cutting 4/12/81 before crime discovered, heard nothing night before, see Vicky Rhodes, found # 6451 on window sill where John used to sleep, saw wht/grn Blazer at Krois'
Seabolt, Paula:
saw green van front of Sharp's @ 2100, sister saw van too, saw green van front of Sharp's 4/11/81
Walke, Chuck:
lived Keddie area, Keddie @ 0330-0400 on 4/12/81 and saw grn pickup w/ two subjects at old gas station, was with Henry Thompson, told different story about same sighting, similar to composite, possible suspect