Hello again,
There are a whole bunch of options, but for pure authenticity, a TCR would have come with a 982cc motor. You can get to a 982 in several ways. I will list them according to the amount of 'pain' involved and the dollars required.
1. Using a 600D block. - Bore to 65mm (may require sleeves), line bore for larger crankshaft main bearing and re-notch for bearing tabs, use A112 70HP crankshaft, notch cylinder bores, narrow cam lobes, remove fuel pump lobe from cam, use 850 rods, special pistons, 600 head. (Would be closest to original) 982cc displacement.
2. Using an 843 block - Bore to 65.5mm, line bore for larger crankshaft main bearing and re-notch for bearing tabs, use a112 70HP crankshaft, notch cylinder bores, narrow cam lobes, remove fuel pump lobe from cam, use A112 camshaft and oil pump drive, 850 rods, special pistons - 996cc displacement
3. Use a 903 block - Bore to 65.5mm line bore for larger crankshaft main bearing and re-notch for bearing tabs, use A112 70HP crankshaft, notch cylinder bores, narrow cam lobes, remove fuel pump lobe from cam, use A112 camshaft and oil pump drive, use A112 rods, but with special pistons. 996cc displacement.
4. Use a 903 block - Same as previous one but use the engine as is, only with the cylinders off-set bored to 67.2mm. 965cc displacement.
5. Use a 1050 block - Aside from some small things, can be used as is. 1047cc displacement.
These are not all the combinations, and there are other issues such as cooling, gearing, axles etc that you will have to work out. It is not a matter of things not working, but rather how robust they are.
There are some safety things that are a MUST.
1. Dual master cylinder.
2. Replace crush spacer between bearings in rear hubs with solid steel spacer
3. Rear swing arm limit straps to limit how much positive camber the rear suspension can generate.
I have 4-5 A112 short blocks (used) as well as heads, cranks etc., both in the USA and in Europe that are available.
Good luck,
Paul Vanderheijden
www.scuderiatopolino.com