Harriers had been shot shy in the first half but came out with an attacking frame of mind in the second period. Substitute striker Ian Foster came close twice before Wrexham doubled their lead
Williams played in Foster on 48 minutes but the substitute's shot was well parried by former Manchester City keeper Dibble.
A minute later Wrexham made their first substitution with Ferguson, son of Manchester United manager Alex, replaced by Barrett.
Dibble had to tip the ball over his bar on 52 minutes from a Foster cross-shot though the Wrexham players felt the ball had already gone out for a goal kick.
The Welsh side added a crucial second goal on 63 minutes through Trundle again to seemingly but the game beyond the home side.
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