So long as your alty doesnt produce more than 400v the alternative you suggested looks ok, the data sheet specifies it has the same trigger current and gate dissipation so it'll probably work, but you just dont know without trying.
While the battery is connected the alty wont produce much more than 12v, its when the battery is disconnected with the engine running that a very high voltage is produced.
A rectifier is only as good as its heatsink, you need to look at the datasheet and work out the dissipation and then work out what size sink you'll need, allthough you can go off the original and use something similar, just **** it and see.
Dont forget to put the thyristors on the sink too, they will dissipate soem energy esp at high revs.
You can make the reg up on veroboard or a pcb, you'd be better putting the thyristors and rectifier on a heatsink and make direct connections, or use some tagstrip to support the legs of the devices from vibration, and build up the smaller components on the veroboard/pcb with a piece of ribbon cable between, commercial units tend to be potted to keep them safe from impact/vibration and cack from the road/track.