Will this bolt directly to my engine bay without modification?

Yes. This tank mounts at OEM attachment points — no drilling, cutting, or adapter brackets needed. Factory bolts work fine.

Does the cap have a pressure seal, or do I need a new one?

Cap is included with a factory-style pressure seal. Inspect the seal before install; if it looks cracked or brittle, replace it with an OEM cap before running coolant.

Can I reuse my old coolant, or do I need to flush the system?

Coolant in good condition can transfer to the new tank — no flush required. If your old coolant shows rust, discoloration, or is over three years old, drain and fill with fresh fluid before install.