Hi Griffstein, welcome to the forum.
Finding the info in one place is proving difficult! What I would say is that BR steam on the South Eastern Division of the Southern Region ended in the early 60s, with Southern Region steam ending completely on 9th July 1967 (the South West Main Line was the last remaining steam section).
Take the Motive Power Depots for example - Stewarts Lane MPD (73A) closed to steam in 1963; Bricklayers Arms (73B) closed to steam in 1962; Hither Green (73C) appears to have lost it's steam allocation in 1962; Faversham (73E) closed to steam in 1959; both Dover (73H) and it's sub-shed at Folkestone Junction closed in 1961; Ramsgate (73G) lost it's steam allocation in 1960. That's not to say that these dates were definitely the end of steam in Kent as occasional workings may still have run, possibly working through from other regions, but this would certainly have been the end of regular steam.
One Bulleid pacific which definitely passed through Kent during this time was rebuilt 'Battle of Britain' No.34100 'Appledore' as this is recorded as working the last steam-hauled 'Golden Arrow' on 11th June 1961.
Some good reference sources include:
Kent Rail -
https://www.kentrail.org.uk/index.htm
which includes pages on specific categories including Dartford station -
https://www.kentrail.org.uk/Dartford.htm
Bulleid light pacifics -
https://www.kentrail.org.uk/bulleid_light_pacific.htm
and Merchant Navy class -
https://www.kentrail.org.uk/merchant_navy_class.htm
BR Locomotive Database -
http://brdatabase.info/sites.php?pag...e=locos&id=517
This link is set for Stewarts Lane Depot (73A) and should be set for the locos allocated which shows all locos allocated to the depot under BR with dates to and leaving the depot.
From this I can see that during the period of 1960 onwards the following Light Pacifics were allocated to 73A:
34001 'Exeter' (from 10/2/61 until 26/5/61)
34004 'Yeovil' (from 10/2/61 until 26/5/61)
34077 '603 Squadron' (until 26/5/61)
34085 '501 Squadron' (until 17/1/61)
34086 '219 Squadron' (until 26/5/61)
34087 '145 Squadron' (until 26/5/61)
34088 '213 Squadron' (until 26/5/61)
34089 '602 Squadron' (until 16/9/63)
34100 'Appledore' (until 16/9/63)
If you repeat the search with other depots on the South Eastern Division such as Hither Green, Ramsgate etc. you should find all the other allocations.
Hope this helps,
Tony