Custom and engineered products have long lead times. The clock often starts only after the architect approves the submittal.
Example: a supplier of motorized gym equipment cannot release the order until the shop drawings are approved. Manufacturing and freight follow.
Ask each supplier for the current lead time and write it in your proposal. Compare it to the project schedule. If the schedule is shorter than the lead time, tell the general contractor before the bid. Late delivery can lead to liquidated damages, depending on the contract.