I would probably say no. Bigger engine should probably require better cooling. I would just take the old one to get repaired.

Also, most places will not cover work after its been transferred between owners. I am not really shocked he turned you away when he found that a previous owner took it there and you were asking about warrantying work you didn't pay for.

Richard E
1989 Montero - Stock-ish
1989 V6 Auto Raider - 5.3 Vortech Swap.
1987 Mitsubishi Starion 2.6t, soon to be 3.5
1983 Honda XL600R