When I first installed the rack on my 69 I used the stock pump with no problems. About June the pump started going bad so I replaced it with a KRC pump. This is the same one that TCP sells but I payed less than half buying it fromThe Car Shop.
You can certainly use a stock pump with the TCP rack. The guys at TCP can tell you what you need to make it work.
The KRC pump is much better and would work better for you in the long run though.
Keep in mind the the TCP pricing on the KRC kit is just that, a "KIT". It may be less expensive elsewhere, but it won't be in kit form, which means you will have to know exactly what you need and once you have all the bits and pieces the price differential is not that great.