Alternator upgrade

[Lapik]

Hi guys. Since our big neighbour here in Estonia is still, I don't really know how to politetely say it, mad, I started to thin about doing some post-apocalyptic conversions to my 2005 1.6 petrol Multistace. I have already fitted a electric coolant heater from Hdi to combat better with our harsh weather, full aluminium skid plate, inverter, 120Ah battery with extended tray, I am also planning on fitting passenger seat from van with box underneath and if I have time, I also stripped a modutop roof stuff which I'd like to transfer too. 

But mi beggest concern also wirh the extra heater is low output of current 90 amp alternator. Has anyone fitted 150A one ftom Hdi's? They share physical fittings, but Im afraid, that belt might slip, as the drive angle is only ca 100 degrees.