The Bedford 4.2 and 5.0 litre engines were both low comp, prefixes were BS and BV respectively. Both had a 2 barrel rochester carb with governer (with adapter for 4BBL valley) and HEI dizzy. They wete really blue motors although introduced in '78/9, but were painted silver. They wete Chev pattern not for the TH400 but for the Eaton 4and 5spd roadranger boxes. They were used to replace the Chev 250 and 292 when I think emissions laws also killed those engines in C20/C30 (which got a 350 SBC). Although it seems a strange place to introduce the blue engine it was only the top end, as by that time all red 4.2/5.0 were 'blue' bottom ends.