Don't even speak of MSRP. Find out how close to invoice price the dealer will get. Then shop other dealers to see what they are offering. Depending on demand for the new models they may sell at or close to invoice, or they may be well above. But at least you will know what their pricing is.
And any manufacturer rebates available should be taken off after you know their sale price relative to invoice.
You can find MSRP and invoice pricing on sites like edmunds.com, nada.com, kbb.com, etc.
And if you plan on trading something in, keep that price negotiation totally separate until you agree on their price for their new truck.
Also check newspaper ads and dealer web sites for special pricing. They will not always tell you of a special ad they are running unless you tell them you saw it.