I think I’d put the strap around the main chassis cross member, underneath the engine – I’ll attach a photograph if I can work out how to do it. A bit of a grovel & probably oily but it ought to be possible to pass the strap underneath the car, around the chassis and back. The ‘filler plates’ attached to the bottom of the radiator and across the chassis makes it difficult / impossible to use anything in front of this cross member. I wouldn’t like to use the cross-tube that supports the front of the body – it might be alright but could bend, or damage the chassis, especially if there’s any corrosion.