The 4-5-7 and 8 plank are all 69mm x 32 mm. 20t mineral length is 86mm x 32mm. Inside depth of 4plank is 11mm. 5plank 15mm 7plank 17mm and 8plank 20mm. Hope that helps.
My link is i still live by the old line, my father worked on it and my granddad was station master at pentre from 1936 till it closed in 1960. So in the 50s i had a real layout at the bottom of the garden.
Not a bad return 57/6 new in 1962 http://www.ebay.co.uk/itm/Tri-ang-OO-gauge-R358-2-6-0-locomotive-Davy-Crockett-tender-boxed-/121172440612?hash=item1c3670b624&nma=true&si=1uLUOhjm%252F0%252BzIJRU0BU5DO1keEw%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557#ht_47wt_1255