I wouldn’t buy that 102 engine if I were you. I don’t believe the hero engine is a Peugeot clone. The 102 engine mounts differently and hangs at a different angle than the hero engine.
You sound like you are willing to do some fab work and welding to get the bike running which is good but if you’re going to make custom mounting and modifications you should get a better engine than that 102 that’s missing the top end and ignition. The 103 is a much better choice