the sp gun is definatley a sexton probably a mk2 with m4 suspension.
if you want 1/43rd ww2 models then the altaya range is very extensive but some are much harder to get hold of, there are numerous ww2 american vehicles like gmc 6x6, dodge wc 4x4, halftracks & jeeps.
not seen an m5/m9 h/track but there is an m3 & m16 half track in the range
the only real outside difference between an m3 & m5 is the m5 has flat mudguards and rounded rear corners, so unless you are really fussy most will not know.
the britsh did have some m3 h/tracks and were used in the sicily landings & early italian front.
great pics btw.