Hello,
What is you vin #? Yes, if it the correct one you may keep the old one. This part does not have a core charge.
1. This part is manufactured by the original supplier to Workhorse, Delco Remy.
2. This is both the starter and the solenoid. We also include the heat shield.
3. There is no core charge, so no need to ship back old part.
4. To calculate shipping charges and sales tax, just add the part to your cart and click on "Estimate Shipping & Taxes", once you select your shipping method it will display the sales tax charge.