There is a company called A-1 electric that makes all kinds of conversion kits.

Here is a link to them

http://www.a1electric.com/catalog/cat_chevtruck.htm

Then here is an item available through Summit that lets you use your original window cranks as the switch.

http://store.summitracing.com/egnsearch.asp?N=400996+317600&autoview=sku